JP6048768B2 - Magnesium alloy material - Google Patents

Description

  The present invention relates to various members such as casings for electric and electronic devices, parts for automobiles, etc., and magnesium alloy materials suitable for materials of these members. In particular, it relates to a magnesium alloy material having excellent corrosion resistance.

  Magnesium alloys containing various additive elements in magnesium have been used as constituent materials for various members such as casings of portable electric and electronic devices such as mobile phones and notebook personal computers and automobile parts.

  Main members made of magnesium alloys are die-cast materials and thixo-mold materials (ASTM standard AZ91 alloy). In recent years, a member obtained by pressing a plate made of a magnesium alloy for extension represented by ASTM standard AZ31 alloy is being used. Patent Document 1 proposes a magnesium alloy plate made of an alloy equivalent to the AZ91 alloy in the ASTM standard and having excellent press workability.

  Since magnesium is an active metal, corrosion resistance such as anodizing treatment or chemical conversion treatment is performed on the surface of the above-mentioned member or a magnesium alloy plate as a material thereof to enhance corrosion resistance.

JP 2007-098470 A

  Magnesium alloys containing Al such as the AZ31 alloy and AZ91 alloy described above tend to have better corrosion resistance as the Al content increases. For example, AZ91 alloy is said to be excellent in corrosion resistance among magnesium alloys. However, the above-described anticorrosion treatment is required even for members made of AZ91 alloy (mainly die-cast material or thixomold material). This is because even when a die-cast material made of AZ91 alloy or the like is not subjected to anticorrosion treatment, local corrosion may occur when a corrosion test is performed as described later. Therefore, further improvement in corrosion resistance is desired for the magnesium alloy material.

  Therefore, an object of the present invention is to provide a magnesium alloy material having excellent corrosion resistance.

  As described above, the corrosion resistance can be improved as the Al content increases. Accordingly, the present inventors have studied magnesium alloys containing various forms of magnesium alloys containing 7.3% by mass or more of Al and investigated the corrosion resistance. As a result, even if the Al content of the entire magnesium alloy material was the same, the corrosion resistance was superior or inferior depending on the form. In order to elucidate the cause, first, the structure of each form was examined. In the magnesium alloy material inferior in corrosion resistance, coarse precipitates (based on additive elements in the alloy. Typically, Al and Mg In the case of a magnesium alloy material having at least one intermetallic compound and having excellent corrosion resistance, fine precipitates are present in a uniformly dispersed state, or substantially no precipitates are present.

  Here, an additive element such as Al in the magnesium alloy exists mainly in at least one state of a precipitate (typically an intermetallic compound), a crystallized product, and a solid solution. When Al is used for precipitates or the like, the amount of Al in the matrix phase of the magnesium alloy constituting the precipitate and the region away from the surroundings decreases.

  The structure in which the coarse precipitate is present is a region where the Al concentration is higher than the surrounding area and the area of this high Al concentration portion is relatively large (mainly the region formed by the precipitate and the surrounding area). It can be said that this organization exists. In other words, it can be said that the region where the Al concentration is relatively low is a local and abundant tissue. And it is thought that corrosion tends to occur in each of the regions where the Al concentration is low, and local corrosion such as pitting corrosion occurs or proceeds.

  On the other hand, a structure in which fine precipitates exist uniformly can be said to be a structure in which the Al concentration is higher than that of the surroundings and a minute region consisting of this high Al concentration portion exists uniformly. In other words, it can be said that fine precipitates are uniformly dispersed and a large amount of Al remaining in the mother phase is uniformly dispersed. The structure substantially free of precipitates consists of a matrix in which Al is substantially uniformly dispersed, and can be said to be a structure in which very fine precipitates are present slightly or not at all. Since Al is uniformly dispersed, local corrosion as described above is unlikely to occur and progress, and a magnesium alloy material having such a structure is considered to have excellent corrosion resistance.

  EPMA (Electron Probe Micro Analyzer) can be preferably used to analyze the Al concentration from the coarse area to the minute area as described above. Therefore, as a result of analyzing the Al concentration for the magnesium alloy materials of the above-mentioned various forms using an EPMA apparatus, as shown in the examples described later, the magnesium alloy material having excellent corrosion resistance contains Al in the entire alloy material. When the amount is x mass%, the area of x mass% ± α occupies half of the area, where there are virtually no locations with very little Al content, and there are also places with very high Al content. We obtained knowledge that there was little target. That is, the present inventors have obtained the knowledge that it is possible to quantitatively specify that the corrosion resistance is excellent by using a parameter such as the area ratio of the Al concentration. In addition, it is considered that this quantitative regulation can be used regardless of the presence form of Al.

  The present invention is based on the above findings, and a magnesium alloy material having excellent corrosion resistance is defined by the Al concentration and its area ratio.

The present invention relates to a magnesium alloy material made of a magnesium alloy containing Al in a range of 7.3 mass% to 16 mass%. This magnesium alloy material satisfies the following (1) to (3) when the content of Al in the entire magnesium alloy material is x mass%.
(1) Area where Al content is (x × 0.8) mass% or more and (x × 1.2) mass% or less is 50 area% or more
(2) Area where Al content is (x × 1.4) mass% or more is 17.5 area% or less
(3) There is substantially no region where the Al content is 4.2% by mass or less

  As described above, the magnesium alloy material of the present invention is substantially free from a region having poor corrosion resistance, such as an Al content of 4.2% by mass or less, and has a high Al concentration (0.8x mass% to 1.2x mass%). In addition, more than half of the area) occupies more than half, and there are few areas with a very high Al concentration (area of 1.4x mass% or more). That is, the magnesium alloy material of the present invention can effectively prevent local corrosion because the region having a low Al concentration does not substantially exist. Further, the magnesium alloy material of the present invention has few or substantially no regions where the concentration of Al is very high (typically, precipitates containing Al etc. are fine and their total abundance is small (form In other words, Al is sufficiently and widely dispersed in the magnesium alloy matrix itself. Thus, the magnesium alloy material of the present invention is in a state in which the Al concentration is uniformly high over at least the entire surface side region. With this configuration, the magnesium alloy material of the present invention is excellent in corrosion resistance.

  As one form of this invention, the form whose said magnesium alloy material is the coil material which wound up the elongate board | plate material is mentioned.

  Since the coil material is composed of a plate material having excellent corrosion resistance, the coil material can be used as a material for a plastic material that is subjected to plastic processing such as press processing, forging processing, and bending processing. It can contribute to mass production of materials. In particular, by setting the plastic working conditions to specific conditions described later, the obtained plastic working material can also maintain the same Al concentration distribution as the coil material, and is excellent in corrosion resistance. Alternatively, the coil material can be rewound and appropriately punched or cut to produce a plate material having a desired shape, which can contribute to mass production of such a plate material. Since the obtained plate material substantially maintains the Al concentration distribution of the coil material, it is excellent in corrosion resistance. The obtained plate material can be used as it is as well as the material of the plastic working material.

  As one embodiment of the present invention, a region where the Al content is (x × 0.8) mass% or more and (x × 1.2) mass% or less is 70 area% or more, and the Al content is (x × 1.4) mass% or more. In which the region is 5 area% or less.

  According to the above embodiment, a region with a high Al concentration (0.8x mass% to 1.2x mass% region) occupies 70% or more, and a region with a very high Al concentration (region of 1.4x mass% or more) is 5%. Al is less than 3% or less depending on the form, depending on the form, so Al is present more uniformly and is more excellent in corrosion resistance.

  As one form of this invention, the said magnesium alloy material has the form which is a plastic working material by which the plastic working was given to the board | plate material.

  The magnesium alloy material of the present invention can take various forms as described later. In particular, since it is a plastic working material formed into a desired shape as in the above-described embodiment, it can be suitably used for various components, housings, and the like. When the above plate material is subjected to a solution treatment (particularly a final solution treatment) as will be described later, because it is excellent in elongation, any plastic work that can be pressed or forged is applied to such a plate material. Compared to die-cast material and thixomold material, it has excellent toughness in addition to corrosion resistance. Alternatively, when the plate material is subjected to plastic processing (primary processing) such as rolling, internal defects such as voids (nests) are reduced or substantially eliminated during processing such as rolling. As a result, the toughness is improved, and the strength is improved by refining crystal grains by rolling or the like. The form in which such plate material is subjected to press working or forging plastic processing (secondary processing) has mechanical properties such as toughness and strength in addition to corrosion resistance, compared to die-casting materials and thixo-mold materials. Also excellent.

  The magnesium alloy material of the present invention is excellent in corrosion resistance.

Fig. 1 is a composition mapping image of a magnesium alloy material by FE-EPMA. Fig. 1 (A) shows sample No. 1: coil material (no final solution), and Fig. 1 (B) shows sample No. 2. : Coil material (with final solution), FIG. 1 (C) is Sample No. 3: Sheet material (rapid heating and quenching material), and FIG. 1 (D) is Sample No. 100: Die casting material. Fig. 2 is a bar graph showing the relationship between the Al concentration and the area ratio (%) of the magnesium alloy material. Fig. 2 (A) shows sample No. 1: coil material (no final solution), Fig. 2 (B ) Is sample No. 2: coil material (with final solution), Fig. 2 (C) is sample No. 3: sheet material (rapidly heated and quenched material), Fig. 2 (D) is sample No. 100: Die casting material. 3 is a micrograph (5000 times) of a magnesium alloy material, FIG. 3 (A) is a sample No. 1: coil material (no final solution), FIG. 3 (B) is a sample No. 2: FIG. 3C shows a coil material (with final solution), FIG. 3C shows Sample No. 3: sheet material (rapid heating / cooling material), and FIG. 3D shows Sample No. 100: die cast material. FIG. 4 is a graph showing the relationship between the Al concentration (mass%) by ICP emission spectroscopic analysis and the X-ray intensity by EPMA in magnesium alloy materials having different Al contents.

Hereinafter, the present invention will be described in more detail.
[Magnesium alloy material]
(composition)
The magnesium alloy constituting the magnesium alloy material of the present invention includes those having various compositions containing an additive element in Mg (remainder: Mg and impurities, Mg: 50% by mass or more). In particular, in the present invention, a high-concentration alloy containing 7.3% by mass or more of an additive element, particularly an Mg—Al alloy containing at least Al as an additive element is used. The higher the Al content, the better the corrosion resistance and the mechanical properties such as strength and hardness. Therefore, a high-concentration alloy having an Al content of 7.3% by mass or more as in the present invention is superior in corrosion resistance and mechanical properties as compared with an alloy having a low Al content. However, if the Al content exceeds 16% by mass, the plastic workability is lowered, so the upper limit is 16% by mass. The Al content is preferably 12% by mass or less, more preferably in terms of plastic workability, particularly 11% by mass or less, and more preferably 8.3% by mass to 9.5% by mass.

  Additive elements other than Al were selected from Zn, Mn, Si, Be, Ca, Sr, Y, Cu, Ag, Sn, Li, Zr, Ce, Ni, Au, and rare earth elements (excluding Y and Ce) One or more elements are listed. When these elements are included, the content of each element is 0.01% by mass or more and 10% by mass or less, and preferably 0.1% by mass or more and 5% by mass or less. Of the above additive elements, at least one element selected from Si, Ca, Sn, Y, Ce, and rare earth elements (excluding Y and Ce) is 0.001% by mass or more in total, preferably 0.1% by mass in total. When it is contained in an amount of 5% by mass or less, heat resistance and flame retardancy are excellent. When the rare earth element is contained, the total content is preferably 0.1% by mass or more, and particularly when Y is contained, the content is preferably 0.5% by mass or more. Examples of the impurity include Fe.

  More specific compositions of Mg-Al alloys include, for example, AZ alloys (Mg-Al-Zn alloys, Zn: 0.2% to 1.5% by mass), AM alloys (Mg-Al-Mn) according to ASTM standards. Alloy, Mn: 0.15 mass% to 0.5 mass%), Mg-Al-RE (rare earth element) alloy, AX alloy (Mg-Al-Ca alloy, Ca: 0.2 mass% to 6.0 mass%), AJ Alloy (Mg—Al—Sr alloy, Sr: 0.2 mass% to 7.0 mass%) and the like. In particular, an Mg-Al alloy containing 8.3 mass% to 9.5 mass% Al and 0.5 mass% to 1.5 mass% Zn, typically AZ91 alloy, is preferable because of its excellent corrosion resistance and mechanical properties.

  In the present invention, the content of Al in the entire magnesium alloy material (hereinafter referred to as Al total average amount): x mass% is the presence state of Al in the magnesium alloy material (mainly precipitates, crystallized materials, and solid solution). Regardless of (at least one), it means the total amount of Al contained in the magnesium alloy material. For the measurement of the total amount, typically, ICP emission spectroscopy (ICP-AES) can be suitably used.

(Al concentration and area ratio (area ratio))
The most characteristic feature of the magnesium alloy material of the present invention is the Al concentration distribution. Specifically, when the Al concentration is analyzed with respect to the surface of the alloy material, (1) the area where the Al content is the Al total average amount (x mass%) ± 20% occupies the majority (however, 7.3 ≦ x ≦ 16). The area below 0.8x mass% (minimum 5.84 mass%) is inferior in corrosion resistance, and the area above 1.2x mass% (maximum 19.2 mass%) has high corrosion resistance in this area itself. The presence of the concentrated concentration makes it relatively easy to have a region inferior in corrosion resistance. On the other hand, the region of 0.8x mass% to 1.2xmass% (hereinafter, this region is referred to as the central composition region) has a small difference in Al concentration, and the area where such Al concentration is uniform is 50 areas. % Or more, it is difficult for a location where the difference in Al concentration is large, that is, a region of less than 0.8x mass% and a region of more than 1.2x mass% as described above. Accordingly, the magnesium alloy material of the present invention has few or less regions inferior in corrosion resistance, and at least the surface side region of the alloy material is constituted by a region where the Al concentration is relatively high, thereby locally Corrosion hardly occurs and has excellent corrosion resistance. The higher the area ratio of the central composition region, the wider the region where the Al concentration is uniform as described above, and the Al concentration tends to be uniform. That is, the Al concentration distribution width tends to be narrow. Therefore, the area ratio of the central composition region is preferably 55 area% or more, particularly 70 area% or more, more preferably 90 area% or more, and particularly preferably 95 area% or more. In addition, when the area of higher Al concentration, specifically, the area of 0.9x mass% to 1.2x mass% is 30 area% or more, the Al concentration is high and the high concentration area exists uniformly. Therefore, it is more excellent in corrosion resistance. Details of the Al concentration measurement method and the area ratio measurement method will be described later.

  The Al concentration can be measured by taking an arbitrary cross section of the magnesium alloy material and an arbitrary portion of the cross section, but the region most involved in corrosion is the surface of the alloy material. Accordingly, at least the surface of the magnesium alloy material of the present invention satisfies the Al concentration distribution defined above. In addition to the form in which the Al concentration distribution inside the magnesium alloy material (for example, the region exceeding 1/4 of the thickness in the thickness direction from the surface) is similar to the Al concentration distribution on the surface, in the present invention, the internal Al concentration The distribution allows a different form from the surface Al concentration distribution.

  In the magnesium alloy material of the present invention, (2) there are few regions where the Al content is Al total average amount (x mass%) × 140% or more (provided that 7.3 ≦ x ≦ 16). In the region of 1.4x mass% (maximum 22.4 mass%) or more, although this region itself has high corrosion resistance, there is a region where Al concentration is relatively low and the corrosion resistance is inferior due to the concentration of Al in this region. It becomes easy to do. On the other hand, in the magnesium alloy material of the present invention, since the region of 1.4x mass% or more (hereinafter, this region is referred to as an ultra-high concentration region) is as small as 17.5 area% or less, there is hardly a region inferior in corrosion resistance. Excellent corrosion resistance. As the area ratio of the ultra-high concentration region is lower, there are fewer regions with a relatively low Al concentration, and the region with poor corrosion resistance can be reduced. That is, the Al concentration distribution width tends to be narrow. Therefore, the area ratio of the ultra-high concentration region is 15 area% or less, more preferably 14 area% or less, particularly 5 area% or less, especially 3 area% or less, and further preferably 1 area% or less. More preferably, the ultra-high concentration region is 0.15 area% or less and ideally does not exist.

  Further, in the magnesium alloy material of the present invention, (3) a region having an Al content of 4.2% by mass or less (hereinafter, this region is referred to as a low concentration region), that is, a region inferior in corrosion resistance as described above. not exist. When there is a location where the Al content is relatively high, corrosion occurs preferentially at a relatively low location or the corrosion proceeds. On the other hand, the magnesium alloy material of the present invention is excellent in corrosion resistance because there are substantially no locations where such an Al concentration is extremely low, that is, locations where corrosion is likely to occur or where corrosion is likely to proceed. “Substantially absent” means that no point of 4.2 mass% or less is observed by EPMA measurement.

(Organization)
As a structure excellent in corrosion resistance, it is desired that a region where the Al concentration is extremely high is small and small, preferably substantially absent. Therefore, depending on the additive element, Al ₁₂ Mg ₁₇ , the structure substantially free of Al-rich precipitates typified by Al-rich intermetallic compounds such as Al ₂ Ca, Al ₄ Ca, Al ₃ Ni, etc. Expected to be the best. However, since the area ratio of the ultra-high concentration region satisfies a specific range and the low concentration region does not substantially exist, it has excellent corrosion resistance. Allow the presence of Al-rich precipitates such as intermetallic compounds. In particular, when Al-rich intermetallic compounds are present, each intermetallic compound is small (average particle size: 3.0 μm or less, preferably 0.5 μm or less) and uniformly dispersed (total area ratio: 11% The following is preferable: Al concentration tends to be uniform. In addition, when Al-rich precipitates such as the above intermetallic compounds are present uniformly, a function as a barrier against corrosion can be expected.

(Form)
As a form of the magnesium alloy material of the present invention, when distinguished from the manufacturing process, a wrought material subjected to a stretching process such as a rolled material and an extruded material (however, there is a solution treatment in the middle of manufacturing), the wrought material is subjected to a correction treatment. Corrected materials, heat treated materials that have been subjected to heat treatment for the purpose of strain removal, etc., solution materials that have undergone final solution treatment, such as wrought materials, straightened materials, and cast materials, and solution treatments Stretched material such as rolling / extrusion (after solution), stretched material, straightened material solution (after solution), straightened material, stretched material such as rolling and the above heat treatment Heat treatment material that has been sequentially subjected to (after solution treatment), and a polishing material obtained by grinding the wrought material / correcting material / heat treatment material / solution treatment material. Furthermore, the plate material in any form of wrought material, straightening material, heat treatment material, solution treatment material, and polishing material is subjected to plastic processing such as drawing, bending, forging and pressing, and mechanical processing such as cutting and punching. Processed materials.

  Among the wrought materials, in particular, the rolled material is refined in crystal grains by rolling, for example, an average crystal grain size of 10 μm or less, further a microstructure of 5 μm or less, or internal defects such as voids (nests) May be a small, small, or substantially non-existing structure (a structure in which a density actually measured with respect to a theoretical density material calculated from a material composition is 99% or more). Having such a fine structure and a structure having a high density can be an index indicating that the material is a rolled material. As described above, the rolled material has few internal defects, is small, or preferably is substantially non-existent, and has excellent mechanical properties such as tensile strength, elongation, and rigidity. Can be suitably used.

  For correction, for example, leveler roll processing or the like can be used. Depending on the degree of straightening, a straightening material by leveler roll processing may have a structure in which a clear grain boundary is difficult to observe even when microscopic observation is performed by introducing a shear band. In this case, since the monochromatic X-ray diffraction peak can be obtained, it is a non-amorphous structure, the monochromatic X-ray diffraction peak can be obtained, and it has a structure in which grain boundaries cannot be observed. It can be an index indicating that Correction materials, especially correction materials by leveler roll processing, tend to recrystallize during plastic processing such as press processing, and tend to be excellent in plastic workability. When the degree of correction is low, the appearance, structure, and mechanical properties may be similar to the rolled material.

Since the solution material is subjected to a solution treatment for generating a supersaturated solid solution, additive elements such as Al exist mainly as a solid solution, Al ₁₂ Mg ₁₇ , Al (MnFe), Al ₂ Ca, Al ₄ Ca, Precipitates such as Al ₃ Ni-containing intermetallic compounds are unlikely to exist, and even if present, they are small and few. Therefore, a small proportion of Al-containing intermetallic compounds can be an indicator of a solution material. Specifically, the ratio of the total area of the intermetallic compound containing at least one of Al and Mg in the cross section of the surface side region of the magnesium alloy material (typically, the region from the surface to 100 μm in the thickness direction) is Those having a content of 3% or less, more preferably 1% or less, can be cited as solution materials. In addition, when the solution material is subjected to a heat treatment of 400 ° C. × 30 hours or more, the hardness tends not to decrease after the heat treatment or the elongation does not substantially change (however, the test The piece shall be ground.) Therefore, it is considered that such a degree of change in mechanical properties before and after the heat treatment can be used as an indicator of the solution material.

  As described above, Al is likely to be uniformly present in the solution material because a supersaturated solid solution is formed throughout the solution material. Specifically, in the case of a solution material that has undergone the final solution treatment, the Al composition has a central composition region of 90 area% or more, an ultrahigh concentration region of 3 area% or less, and further 1 area% or less. Therefore, the solution material is superior in corrosion resistance. In addition, the solution material is excellent in plastic workability because there are substantially no defects such as coarse precipitates (typically, intermetallic compounds) that become the starting point of cracking during plastic working. Therefore, this solution material can be suitably used as a material for plastic working material.

  The abrasive has a smooth surface and excellent surface properties. Therefore, a small surface roughness (for example, a maximum height Rz of 20 μm or less) or the presence of polishing traces is an indicator of an abrasive.

  Although the heat treatment material depends on the heat treatment conditions, for example, (1) no shear band is observed inside the magnesium alloy material, (2) the proportion of particles having a crystal grain size of 0.1 μm or less in the cross section is 5 area% or less It can be considered that this can be an index indicating that it is a heat treatment material.

  In the case where the above-described processed material is a plastic processed material, the plastic processed material also has a central composition region by using a form in which the magnesium alloy material of the present invention is a plate material and performing plastic processing under specific conditions. Has an Al concentration distribution of 50 area% or more, an ultra-high concentration area of 17.5 area% or less, and a low concentration area substantially not present, and is excellent in corrosion resistance. That is, this plastic working material can substantially maintain the Al concentration distribution of the material. The machined material described above can substantially maintain the Al concentration distribution of the material.

  On the other hand, when distinguishing the form of the magnesium alloy material of the present invention by shape, a plate material (consisting of a substantially front and back parallel plane and side surfaces connecting the front and back surfaces, the distance between the front and back (= thickness) Is a substantially uniform shape throughout, and when viewed in plan, it can typically take a rectangular shape, as well as various other planar shapes such as a circular shape, an elliptical shape, a polygonal shape, etc.), long Examples thereof include a coil material obtained by winding a simple plate material, and various irregular shapes excluding the plate material. Examples of the irregular shape include an arbitrary three-dimensional shape that can be formed by a die casting method or a thixomold method, and a three-dimensional shape that can be formed by plastic working such as press working. The three-dimensional shape body, for example, has a protrusion such as a rib or a concave groove integrally on a part of a plate material, a shape partially different in thickness, a cross section used for a housing of various devices, etc.] And a relatively simple shape such as a polygonal columnar body such as a spherical body, an ellipsoidal body, and a triangular columnar body. Further, the irregularly shaped body may have a form including a through hole (including a large one such as a window) in a part thereof. Such a concavo-convex shape or a shape having a through hole can be easily formed by using a die casting method or the like. A material obtained by forming an ingot or the like into a desired shape by cutting or grinding may be used. In addition, examples of the irregularly shaped body include a form having a plastic working part in which plastic working such as press working is performed on a part thereof.

  The magnesium alloy material of the present invention can take various shapes as described above, but if it is a coil material, the magnesium alloy material can be suitably used as a material for a plastic work material subjected to plastic working such as press work. It can contribute to mass production of plastic working materials. When the magnesium alloy material of the present invention is a coil material, more specific forms include a solution coil material obtained by subjecting a rolled coil material, a cast coil material, or a rolled coil material to a final solution treatment. These coil materials include, for example, those having a thickness of 10 mm or less, further 5 mm or less, a width of 100 mm or more, further 200 mm or more, particularly 250 mm or more, a length of 30 m or more, further 50 m or more, particularly 100 m or more. Such a long material and a wide material are suitable for the material of the plastic working material as described above. In particular, a rolled material or a material obtained by subjecting the rolled material to a final solution treatment can have a form with a thinner thickness or a longer length as compared with the cast material. For example, a thin material having a thickness of 2 mm or less, particularly 1.5 mm or less, particularly 1 mm or less, or a long material having a length of 50 m or more, further 100 m or more, particularly 200 m or more can be used. Thin-walled materials with a thickness of 2 mm or less can be suitably used as a material for thin and lightweight plastic working materials. However, the thickness is preferably 0.1 mm or more, and 0.3 mm to 1.2 mm is easy to use.

  Since the magnesium alloy material of the present invention is excellent in corrosion resistance, it is expected that the magnesium alloy material can be used satisfactorily even if it is not subjected to anticorrosion treatment such as chemical conversion treatment or anodizing treatment depending on the corrosive environment. In this case, the anticorrosion process can be reduced, the productivity of the magnesium alloy material can be increased, and waste can be reduced, so that it is expected that the environmental load can be reduced. Of course, the magnesium alloy material of the present invention can be in a form in which an anticorrosion treatment such as a chemical conversion treatment or an anodizing treatment is performed, that is, a form having an anticorrosion layer. When the surface is provided with an anticorrosion layer, the Al concentration can be measured by removing the anticorrosion layer by polishing or cutting and exposing the surface of the base material made of a magnesium alloy without performing high-precision cross-sectional observation. When the coating layer is provided in addition to the anticorrosion layer, the corrosion resistance can be further improved, and the commercial value can be improved by coloring or applying a pattern. An anticorrosion layer and a coating layer are good to apply to a desired location.

[Production method]
In order to produce the magnesium alloy material of the present invention, it is essential to perform solution treatment at least once before obtaining the final product. In particular, in the case of a manufacturing method including a warm rolling step, in addition to including a solution forming step, the cooling rate until the material is brought to a specific temperature in a cooling step after the final warm rolling is in a specific range. It is possible to use a manufacturing method controlled to Or the manufacturing method which controls the cooling rate of a specific temperature range to a specific range can be utilized in the final solution treatment process irrespective of the presence or absence of a warm rolling process. For example, the production method of the magnesium alloy material of the present invention includes a form having a rolling process (manufacturing method 1-1 to 1-5) and a form not having a rolling process (manufacturing method 2). In each production method described below, at least one step is deleted in the range where the magnesium alloy material of the present invention having a specific Al concentration distribution that satisfies the above conditions (1) to (3) is obtained, The order of each process can be changed.

(Production method 1-1)
When the magnesium alloy material of the present invention is used as a rolled material, for example, it can be manufactured by a manufacturing method including the following preparation process, intermediate solution forming process, and rolling process.
Preparation step: a step of preparing a cast material made of a magnesium alloy containing Al of 7.3 mass% to 16 mass% and manufactured by a continuous casting method.
Intermediate solution treatment step: A step of producing an intermediate solution material by subjecting the cast material to a solution treatment of holding temperature: not less than the minimum holding temperature below and holding time: not less than 1 hour and not more than 25 hours.
Minimum holding temperature: Temperature that is 10 ° C lower than the temperature at which Al dissolves in Mg (solidus temperature) in the Mg-Al binary phase diagram (mass%) Rolling process: More than 1 pass to the intermediate solution material A process of producing rolled material by performing warm rolling.
In particular, in the manufacturing process after the intermediate solution process, the total time for maintaining the material to be processed (typically rolled material) in a temperature range of 150 ° C. or higher and 300 ° C. or lower within 12 hours, and 300 The thermal history of the material is controlled so that it is not heated to a temperature higher than ° C.
And, in the rolling process, after the final warm rolling, the average cooling rate from the temperature of the material when starting cooling to the temperature of the material becomes 100 ° C or less is 0.8 ° C / min or more And

In the binary phase diagram (% by mass) of the above-mentioned minimum holding temperature: Mg-Al, a temperature that is 10 ° C. lower than the solidus temperature is typically expressed as follows (also described later in production method 1-2) The same). Al total average amount in magnesium alloy: When x mass% is 5 mass% or more and 13 mass% or less, the solidus temperature is 283 ° C to 437 ° C, and the solidus temperature increases with the increase of Al total average amount The minimum holding temperature is expressed by the following linear expression.
(Formula) (Minimum holding temperature) = 20 × x + (182-10) = 20x + 172
On the other hand, when the Al total average amount is more than 13 mass% and 16 mass% or less, the minimum holding temperature is (437-10) ° C. = 427 ° C.

In the production method 1-1, in particular, in the steps after the intermediate solution treatment, preferably until the final product, the total time for keeping the material in the temperature range of 150 ° C. to 300 ° C. is shortened to 12 hours or less. The temperature range of 150 ° C. to 300 ° C. is a temperature range in which an Al-rich intermetallic compound such as Al ₁₂ Mg ₁₇ is easily grown. By setting the holding time in this temperature range to a relatively short time as described above, particularly the growth of the intermetallic compound is suppressed, and the increase in the ultrahigh concentration region and the low concentration region is suppressed. And, when the cooling state is adjusted so that the specific cooling rate is at least 100 ° C. in the cooling step so that Al diffusion does not substantially occur after the final warm rolling, the intermetallic compound Growth can be suppressed, and an increase in the ultra-high concentration region and the low concentration region can be suppressed. Increasing the cooling rate is preferable because the increase in the ultrahigh concentration region and the low concentration region can be suppressed. Furthermore, the growth of the intermetallic compound is also suppressed by preventing the heating above 300 ° C.

(Production method 1-2)
When the magnesium alloy material of the present invention is used as a solution material that has undergone a rolling process, for example, the magnesium alloy material can be manufactured by a manufacturing method including the following preparation process, intermediate solution process, rolling process, and final solution process. .
Preparation step: a step of preparing a cast material made of a magnesium alloy containing Al of 7.3 mass% to 16 mass% and manufactured by a continuous casting method.
Intermediate solution treatment step: A step of producing an intermediate solution material by subjecting the cast material to a solution treatment of holding temperature: not less than the minimum holding temperature below and holding time: not less than 1 hour and not more than 25 hours.
Minimum holding temperature: Temperature that is 10 ° C lower than the temperature at which Al dissolves in Mg (solidus temperature) in the Mg-Al binary phase diagram (mass%) Rolling process: More than 1 pass to the intermediate solution material A process of producing rolled material by performing warm rolling.
Final solution treatment step: a step of subjecting the rolled material to a final solution treatment of holding temperature: above the minimum holding temperature and holding time: from 1 hour to 40 hours.
In particular, in the final solution treatment step, the cooling rate in the temperature range of 330 ° C. to 380 ° C. satisfies the following.
When a region from the surface of the rolled material to 10 μm in the thickness direction is a surface layer region, the surface layer region is cooled at 1 ° C./min or more.

  By applying the final solution treatment after rolling as described above, precipitates such as Al-rich intermetallic compounds produced up to the rolling process are solid-dissolved to increase the ultra-high concentration region and the low concentration region. It can be effectively suppressed. In the rolling step of the manufacturing method 1-2, the cooling rate after the final warm rolling may be set to a specific range in the same manner as in the manufacturing method 1-1 described above. Also in this production method 1-2, until the final product is obtained after the final solution treatment step, the total time for maintaining the temperature range of 150 ° C. or more and 300 ° C. or less is as short as possible, and more than 300 ° C. It is preferable to control the heat history of the raw material so that it is not heated to a temperature, because the Al concentration distribution of the solution material obtained through the final solution treatment step can be maintained.

(Production method 1-3)
The rolled material manufactured by the above-described manufacturing method 1-1 can be subjected to a final heat treatment for the purpose of distortion removal. That is, when the magnesium alloy material of the present invention is a heat treatment material that has undergone a rolling process, in addition to the preparation process, intermediate solution forming process, and rolling process of the production method 1-1, a production method that includes a final heat treatment process described later. Can be manufactured.

(Production method 1-4)
Alternatively, the rolled material or solution material produced by the production methods 1-1 and 1-2 may be subjected to correction (typically warm correction) for the purpose of increasing straightness or the surface properties. Cleaning and polishing can be performed for the purpose of improvement (removal of oxide layer, surface defects, lubricant used in rolling, etc.) and the like. In particular, when the magnesium alloy material of the present invention is used as an orthodontic material or an abrasive, a preparation process, an intermediate solution forming process, a rolling process (process specified in the manufacturing method 1-1 or 1-2), a final solution forming process (manufacturing method) In addition to the steps defined only for 1-2, it can be produced by a production method comprising at least one of a correction step and a polishing step described later.

(Product form of production method 1-1 to 1-4)
A manufacturing method comprising the above preparation step, intermediate solution forming step, rolling step, and further comprising at least one step selected from a final solution forming step, a final heat treatment step, a straightening step, a polishing step and a cleaning step. In the manufacturing method, a plate material having a predetermined length (a short plate material considered to be difficult to wind (for example, a length of 5 m or less, particularly 1 m or less), hereinafter referred to as a sheet material), or a long plate material is obtained. It is done.

  The sheet material is obtained, for example, by cutting the cast material into a predetermined length in the preparation step to obtain a cast material (cast plate) having a predetermined length, and using the cast material as a raw material through subsequent steps. Alternatively, a sheet material can be obtained by winding a long cast material in the preparation step to produce a cast coil material, producing a coil material in each step, and finally cutting it to a predetermined length. On the other hand, when not performing the said cutting | disconnection, a elongate board | plate material is obtained and this invention magnesium alloy material of the form of a coil material is obtained by winding up this elongate board | plate material. When producing a coil material, in each process after a preparatory process, feeding and winding of a coil material are generally performed. In this case, since the material provided to each process is a coil material in which a long material or a wide material is wound up, a large amount of material is transferred or heated at a time, and processing of each process is continuously performed. Because it can be done, it is excellent in productivity of magnesium alloy material. The magnesium alloy material of the present invention can be produced by using either a sheet material or a coil material as a material for each step.

(Production method 1-5)
Alternatively, when the magnesium alloy material of the present invention is used as a plastic working material by subjecting any of the rolled material, solution heat treating material, heat treating material, straightening material, polishing material, and cleaning material to plastic working, each of the manufacturing methods described above Furthermore, it can manufacture by providing the following plastic working processes.
Plastic processing step: Pre-heating the obtained plate material at a holding temperature: 350 ° C. or less (preferably 300 ° C. or less) and a holding time: 8 hours or less (preferably 0.5 hour or less), and plastic processing is performed on this heated plate material The process of applying.

Hereinafter, each process of the manufacturing method 1-1 to 1-5 will be described in more detail.
≪Preparation process≫
The cast material preferably uses a continuous casting method. The continuous casting method can stably obtain a cast material of uniform quality in the longitudinal direction and can be rapidly solidified, so it can reduce oxides and segregation, and can also be the starting point of cracking during rolling. As a result, it is possible to suppress the formation of coarse crystal precipitates exceeding 10 μm, which can be obtained, and a cast material excellent in plastic workability such as rolling and extrusion can be obtained. In particular, the twin roll continuous casting method is easy to form a plate-shaped cast material with little segregation. The cross-sectional area, thickness, width, and length of the cast material are not particularly limited, but segregation is likely to occur if it is too thick. Therefore, the thickness is preferably 10 mm or less, more preferably 7 mm or less, and particularly preferably 5 mm or less. In addition, if a long cast material with a length of 30 m or more, 50 m or more, especially 100 m or more, or a wide cast material with a width of 100 mm or more, 250 mm or more, especially 600 mm or more is used as the material of the rolled material, the long Simple rolled plates and wide rolled plates can be produced. The cast material may be a cast coil material wound in a coil shape, or may be a cast sheet material cut into a predetermined length, and may be appropriately selected according to a desired form. When the inner diameter of the cast coil material is small when winding it in a coil shape, it can be wound up without cracking when it is heated to 150 ° C or more just before winding the cast material, and the cast coil material can be easily Can be made.

≪Intermediate solution process≫
A material that is excellent in plastic workability such as rolling and extrusion by reducing the presence of coarse precipitates by applying an intermediate solution treatment to the above cast material to homogenize the composition and dissolving elements such as Al. It can be. The holding temperature of the intermediate solution treatment is typically 350 ° C. or higher and 450 ° C. or lower, particularly 380 ° C. or higher, and more preferably 390 ° C. or higher and 420 ° C. or lower. The holding time is 1 hour to 25 hours, particularly 10 hours to 25 hours. The holding time is preferably increased as the Al content increases. Further, in the cooling step from the holding temperature, if the cooling rate is increased by using forced cooling such as water cooling or blast as in the final solution treatment described later (preferably 1 ° C./min or more, more preferably 50 ° C./min or more), which is preferable because growth and precipitation of precipitates can be suppressed.

  The cast material may be subjected to an intermediate solution treatment as it is, but before the intermediate solution treatment is performed, rolling with a small reduction ratio (a reduction ratio of about 1% / 1 pass to 15% / 1 pass) Alternatively, surface grinding may be performed.

≪Rolling process≫
When rolling the magnesium alloy, if the temperature of the material is room temperature, it is difficult to increase the rolling reduction, resulting in a decrease in production efficiency. Therefore, considering productivity, it is preferable to perform at least one pass warm rolling. . Heating the material (intermediate solution material or rolled material during rolling) can improve the plastic workability such as rolling, and the higher the material temperature, the more the plastic workability can be improved. Precipitates such as intermetallic compounds are coarsened, leading to an increase in the ultra-high concentration region and the low concentration region, and a coarse precipitate causes a decrease in plastic workability. Accordingly, the temperature of the material is preferably 300 ° C. or lower, particularly 150 ° C. or higher and 280 ° C. or lower. The material can be heated using a heating means such as an atmospheric heating furnace by providing a preheating step. As the heating furnace, an appropriate one that can store a material (a sheet material or a coil material) can be used.

  In particular, when rolling the cast sheet material to produce a rolled material (sheet material), and the obtained rolled material is the magnesium alloy material of the present invention having the specific Al concentration distribution, the holding temperature of the preheating step It is preferable to shorten the holding time. Here, as described above, when the material is controlled so as to be as short as possible (preferably within 12 hours) when the material is maintained in a specific temperature range: 150 ° C. to 300 ° C. at the time of rolling, precipitates ( In particular, the growth of the Al-rich intermetallic compound) can be effectively suppressed, and an increase in the ultra-high concentration region and the low concentration region can be prevented. In coil materials wound up with a long or wide material, when trying to heat the entire coil material to a uniform temperature, at least a part of the coil material is kept in the specific temperature range during preheating. Tend to be longer. In particular, even when a long or wide material is used, the entire coil material is heated evenly when the material is wound closely to reduce the gap between turns in order to make a small coil material. It takes a certain amount of time to complete. Therefore, there may be a region where the time for which the specific temperature range is maintained is long. In order to suppress the growth of precipitates over the entire coil material, it is desirable to adjust the size of the coil material or shorten the preheating time so that the preheating time is also included in the total time. It is. As a method for shortening the preheating time, for example, an in-line heating device (typically a heating device using radiant heat, current heating, induction heating, etc.) is provided immediately before the rolling device to perform rapid heating. Is mentioned. By making it in-line, the time until rolling after heating can be shortened. In addition, as a method for shortening the time during which the material is maintained at 150 ° C. to 300 ° C., after passing through a rolling device (typically, a rolling roller), the rolled material is rapidly cooled by being immersed in a refrigerant or a lubricant. (Preferably a cooling rate of 1 ° C./sec or more). When both the rapid heating and the rapid cooling are performed, the time during which the material is held at 150 ° C. to 300 ° C. in the rolling process can be effectively shortened. In particular, the rapid heating and rapid cooling can be easily performed when the material to be rolled is a short material such as a cast sheet material. In addition, for example, even when preparing and stacking a plurality of materials and heating them at once, the time for heating each material to a uniform temperature is relatively short by providing an appropriate gap between the materials. it can. This technique can also be easily applied when the material to be rolled is a short material such as a cast sheet material. For example, when producing a rolled material (sheet material) having a predetermined length and having a specific Al concentration distribution that satisfies the above conditions (1) to (3), warm rolling of one pass or more is performed. When applied, the total holding time in the preheating before rolling is preferably 0.01 hours or more and 8 hours or less, and particularly preferably 0.01 hours or more and 0.3 hours or less. By controlling the preheating conditions in this manner, a magnesium alloy material that is substantially free of precipitates and has a narrower Al concentration distribution width, that is, a magnesium alloy material that is superior in corrosion resistance can be obtained.

  The rolling including the warm rolling may be performed in one pass or multiple passes. By rolling a plurality of passes, a rolled material with a small thickness is obtained, and the average crystal grain size of the structure constituting the rolled material is reduced (for example, 10 μm or less, preferably 5 μm or less), or press working. It is possible to improve the plastic workability. The number of passes, the reduction rate of each pass, and the total reduction rate can be appropriately selected so that a rolled material having a desired thickness can be obtained. In addition, known rolling conditions, for example, appropriate conditions such as heating not only the raw material but also the rolling roll may be used.

  In particular, when producing a rolled material (sheet material) or a rolled coil material having a specific Al concentration distribution that satisfies the above conditions (1) to (3), the final warm rolling was performed. In the subsequent cooling step, it is preferable that the average cooling rate from the temperature of the material at the start of cooling until the temperature of the material reaches at least 100 ° C. is 0.8 ° C./min or more. By cooling the material quickly after the final warm rolling, it is possible to effectively prevent precipitates from growing during cooling and increasing the ultra-high concentration region and the low concentration region. In particular, in the case of a coil material, since the heated state as described above is easily maintained for a long time, it is possible to quickly cool after the final warm rolling, which generates or increases an ultra-high concentration region or a low concentration region. Effective for suppression. The average cooling rate is, for example, the temperature of the raw material when starting cooling after the final warm rolling, and the time t (min) from the obtained measurement temperature: Tmp (° C.) to 100 ° C. Is set to a speed represented by (Tmp-100) / t (° C./min). The cooling state may be adjusted so that (Tmp-100) / t (° C./min)≧0.8 (° C./min). The material temperature may be measured using either a contact sensor such as a thermocouple or a non-contact sensor such as a thermography. It is recommended to prepare an extremely thin thermocouple and place it on the surface of the material.

  The cooling rate is preferably as high as possible, and is preferably 1 ° C./sec or more, and more preferably 5 ° C./sec or more. In the cooling step, any cooling means that can achieve the cooling rate can be used. In particular, if forced cooling is used, the cooling rate can be increased. There are various forced cooling means, such as those that use a gaseous medium such as a fan (air cooling) or blast (jet air cooling), those that use a liquid medium such as water cooling, and those that use a solid medium such as a cooling roll. Can be used. In particular, when air cooling such as blast is used, it is possible to obtain an effect that a step of removing the liquid refrigerant adhering to the material is unnecessary, and the surface properties are not deteriorated due to the adhesion of the liquid refrigerant. On the other hand, when the liquid refrigerant is used, it is easy to increase the cooling rate. It is preferable to use a liquid refrigerant that includes a cleaning agent (for example, a surfactant) that can remove the lubricant used in rolling or the like because cooling can be performed together with cooling. The forced cooling means may be arranged off-line, but if arranged in-line, a large contact area between the material surface and the cooling medium can be secured, so that the cooling efficiency can be improved. In the case of a coil material, after the final warm rolling, the cooling may be performed after winding. In the case of a coil material, the cooling may be performed in a wound state, but if it is performed in a rewinded state, the cooling rate can be easily increased. If the cooling rate can be achieved, natural cooling may be performed without using the forced cooling means.

  In addition, when performing rolling with a small rolling reduction by finish rolling etc., it can be set as cold work. In the cold working, the Al concentration is hardly changed, and the Al concentration distribution before the cold working is substantially maintained.

  When rolling a plurality of passes, an intermediate heat treatment can be performed between passes within a range in which the holding time in the temperature range of 150 ° C. to 300 ° C. described above is included in the total time. By the intermediate heat treatment, strain, residual stress, texture, etc. introduced into the material by plastic working (mainly rolling) up to the heat treatment can be removed and reduced. By carrying out like this, careless cracking, distortion, and a deformation | transformation can be prevented by the rolling after the said heat processing, and rolling can be performed more smoothly. The holding temperature of the intermediate heat treatment material is also preferably 300 ° C. or lower. The holding temperature is preferably 150 ° C. or higher, particularly 250 ° C. or higher and 280 ° C. or lower. The holding time is, for example, about 0.5 hour to 3 hours. Also in the cooling step after the intermediate heat treatment, it is preferable to increase the cooling rate (preferably 1 ° C./min or more, more preferably 50 ° C./min or more) because the growth of precipitates can be suppressed.

  As described above, the thickness, width, and length of the rolled material can be appropriately selected. Moreover, when the said rolling uses suitably a lubricant, the frictional resistance at the time of rolling can be reduced, the burning of a raw material etc. is prevented and it is easy to perform rolling. Furthermore, when a roll having a groove on the outer periphery of the roll is used as a rolling roll, a rolled material having a groove can be manufactured by using a rolled material having a rib, and a roller having a protrusion on the outer periphery of the roll. In addition, the obtained rolled material can be cut or ground to form a desired uneven shape or stepped shape, or a boss or a through hole can be formed.

≪Final solution treatment≫
By performing the final solution treatment after the rolling, the precipitate can be re-dissolved, the ultra-high concentration region can be sufficiently reduced, and the low concentration region can be substantially absent. If the holding temperature is less than the above-mentioned minimum holding temperature or the holding time is less than 1 hour, a supersaturated solid solution cannot be sufficiently produced, and it is difficult to sufficiently reduce the ultrahigh concentration region. If the holding temperature is too high (typically over 450 ° C) or the holding time is over 40 hours, it is an energy loss to heat the matrix even after it has been seized or becomes sufficiently solid solution. Since the productivity may be lowered, the holding temperature is preferably set to a low value. For example, 390 ° C. or more and 420 ° C. or less and holding time: 10 hours or more and 25 hours or less can be mentioned.

And when performing the last solution treatment, in the cooling process from the said holding temperature, a cooling rate is adjusted so that the cooling rate in the temperature range of 330 to 380 degreeC may become 1 degreeC / min or more. Here, in a magnesium alloy containing a large amount of Al such that the Al content is 7.3% by mass or more, precipitates such as Al-rich intermetallic compounds such as Al ₁₂ Mg ₁₇ are likely to occur in the temperature range of 330 ° C. to 380 ° C. It is said. Therefore, it is desirable to pass through this temperature range as quickly as possible. Therefore, in the production of the magnesium alloy material of the present invention having an Al content of 7.3% by mass or more, the cooling rate in the temperature range of 330 ° C. to 380 ° C. is increased as described above to pass through a temperature range where precipitates are likely to occur. By shortening the time to perform, the precipitation of the intermetallic compound is suppressed, and the increase of the ultra-high concentration region and the low concentration region accompanying the generation of the precipitate is suppressed. The cooling rate is preferably as high as possible, and is preferably 1 ° C./min or more, and more preferably 50 ° C./min or more.

  It is sufficient that at least the surface layer region of the rolled material to be processed satisfies the cooling rate. As described above, corrosion occurs and proceeds from the surface of the magnesium alloy material. Therefore, since the surface layer region in the magnesium alloy material is excellent in corrosion resistance, that is, it is only necessary to have a specific Al concentration distribution that satisfies the above conditions (1) to (3), the surface layer region to be processed Is cooled at least at the above cooling rate. Specifically, forced cooling as described above can be suitably used. In particular, when air cooling such as blast using a blast means such as a fan or a jet jet mechanism of cold air is used, it is difficult to oxidize and there are few cooling spots. The effect of suppressing the deterioration of the surface properties accompanying the adhesion of is obtained. On the other hand, when a liquid refrigerant is used, a cooling method such as mist spraying, spraying water, or immersion in a liquid refrigerant that sprays a liquid refrigerant such as water or a reducing liquid can be used. In addition, when straightening is performed after the final solution treatment or plastic processing such as pressing is performed, a lubricant is used as a liquid refrigerant, and cooling is performed by applying the lubricant to the solution material or immersing it in the lubricant. May be. When it is desired to remove the lubricant used for rolling or the like, a liquid refrigerant containing a cleaning agent as described above may be used as the forced cooling means. Water cooling using a liquid refrigerant can increase the cooling rate more than air cooling. In the case of a coil material, it may be cooled as it is, but if it is rewound, it is easy to increase the cooling rate. Depending on the thickness of the plate material that constitutes the coil material, for example, when cooling by the jet ejection mechanism in the unwound state, the cooling rate is about 50 ° C./min, and when performing water cooling, the cooling rate is about 400 ° C./min. be able to. It is good to wind up after cooling to about room temperature. In addition, since the plate material (including the cast material) that has undergone the final solution treatment process is also excellent in plastic workability, it can be sufficiently wound even at a room temperature of about a winding diameter that is industrially used.

  The cooling rate is determined by measuring the surface temperature of the material after the final solution, setting the time (min) so that the cooling rate in the temperature range of 330 ° C. to 380 ° C. is the desired rate, The cooling state may be adjusted so that Here, since the magnesium alloy is excellent in thermal conductivity, the temperature of the region (surface region) from the surface to the thickness direction of 10 μm is synonymous with the temperature of the outermost surface. Accordingly, the cooling rate of the surface region can be set by measuring the temperature of the outermost surface of the material and measuring the temperature. For the measurement of the temperature of the outermost surface of the material, any of the above-described contact sensors such as thermocouples and thermography and non-contact sensors can be used.

≪Final heat treatment≫
When the final heat treatment is performed after rolling, the holding temperature is preferably 300 ° C. or lower. More specific conditions include a holding temperature: 100 ° C. to 300 ° C. and a holding time: 5 minutes to 60 minutes. The time for holding the material (rolled material) in the temperature range of 150 ° C. or higher and 300 ° C. or lower in the final heat treatment step is preferably included in the total time, and the holding time is preferably less than 30 minutes. By having such a specific condition, a rolled material having a specific Al concentration distribution that satisfies the above conditions (1) to (3), and reduced or removed distortion during rolling, etc. can do.

≪Correction≫
The flatness of the plate material can be improved by performing correction after rolling or after the final solution treatment. The correction can be carried out at room temperature or a temperature below room temperature, but if it is carried out warm, the flatness can be further improved. When performing warm correction, the holding temperature is preferably 300 ° C. or lower. More specific conditions include a holding temperature: 100 ° C. or higher and 300 ° C. or lower, preferably 150 ° C. to 280 ° C. It is preferable that the total time includes the time for holding the material (for example, rolled material) in the temperature range of 150 ° C. or more and 300 ° C. or less in the straightening process. Warm correction is, for example, a heating furnace capable of heating a material, and a roll unit in which a plurality of rolls are arranged in a staggered manner so as to bend (strain) the heated material continuously. A roll leveler device comprising: When a roll leveler is used, even a long material can be continuously corrected. In addition, for warm correction, for example, a warm press device can be used. Even after warm straightening, if the average cooling rate from the temperature of the material at the start of cooling to the temperature of the material reaches 100 ° C or less is 0.8 ° C / min or more, it is extremely high due to the growth of precipitates. An increase in the amount of precipitates such as an increase in the concentration region and the low concentration region and an Al-rich intermetallic compound can be effectively suppressed. In order to achieve this cooling rate, the forced cooling means may be appropriately used as described above, or natural cooling may be used. In particular, when performing warm correction continuously from rolling, if the cooling rate is controlled as described above, the Al concentration distribution can be made to be in a specific state, and even when wound in a coil shape, curling is not possible. A plate material that is difficult to stick and is excellent in flatness is preferable.

≪Plastic processing≫
When plastic processing such as press processing is performed on the sheet material or coil material manufactured as described above, the plastic workability can be improved by heating the material such as the sheet material or the coil material. The temperature of the material is preferably 350 ° C. or lower, more preferably 300 ° C. or lower, and particularly preferably 280 ° C. or lower. In particular, 150 ° C. or higher and 280 ° C. or lower, and more preferably 150 ° C. or higher and 220 ° C. or lower are preferable. In preheating the material to the temperature, by setting the holding time to 8 hours or less as described above, it is possible to suppress the growth of precipitates and effectively prevent an increase in the ultrahigh concentration region and the low concentration region. If the material is heated to such an extent that desired plastic working is possible, the holding time is preferably as short as possible, 0.5 hours or less (30 minutes or less), and more preferably 0.3 hours or less. In particular, as described above, the coil material may require a longer time for making the entire temperature uniform than that of the sheet material. An apparatus can be used, or a fan or a wind guide plate can be appropriately disposed in the heating furnace. On the other hand, although the time itself during the plastic working such as press working depends on the shape, it is considered to be as short as several seconds to several minutes in the press working, and it is considered that defects such as coarsening of precipitates do not substantially occur. By performing plastic working under such specific conditions, it is possible to obtain a plastic work material having a specific Al concentration distribution that satisfies the conditions (1) to (3) described above.

  Heat treatment can be performed after the plastic working to remove strain and residual stress introduced by the plastic working and improve mechanical characteristics. The heat treatment conditions include a holding temperature: 100 ° C. to 300 ° C. and a holding time: about 5 minutes to 60 minutes. However, also in this heat treatment, it is preferable that the holding time in the temperature range of 150 ° C. to 300 ° C. is included in the total time.

≪Total time to keep the material in a specific temperature range≫
After the intermediate solution treatment as described above, preferably in the process up to the final product (rolling (including intermediate heat treatment), final heat treatment, straightening, preheating before plastic working, etc.), the material is 150 ° C ~ 300 It is preferable to control the total time kept in the temperature range of ° C to a relatively short time of 12 hours or less. In the case of performing the final solution treatment, it is preferable that the total time for keeping the material in the temperature range of 150 ° C. to 300 ° C. is 12 hours or less in the steps from the final solution treatment to the final product.

  In order to ensure a sufficient heating time for plastic working such as rolling, the total time of maintaining the temperature range of 150 ° C. to 300 ° C. is preferably 0.01 hours or more. More preferably, the temperature range: 150 ° C. or more and 280 ° C. or less, more preferably 150 ° C. or more and 220 ° C. or less, the total time: 8 hours or less, particularly 0.3 hours or less, the processing degree of each pass in the rolling process Control manufacturing conditions such as total processing degree, preheating conditions (such as preheating means and time), cooling process conditions (such as cooling means and time), and line speed. Moreover, since the Al-rich intermetallic compound described above tends to precipitate as the Al content increases, the total time is preferably adjusted according to the Al content.

  After the intermediate solution treatment as described above, when performing the final solution treatment, it is preferable not to heat to more than 300 ° C. after the final solution treatment, but a short time that does not cause coarsening of precipitates ( Preferably 8 hours or less, more preferably 1 hour or less).

  As a manufacturing method including a rolling process as described above, as a more specific manufacturing method, for example, casting → intermediate solution (preferably, cooling rate is controlled in the cooling process) → rolling → intermediate heat treatment (cooling depending on the holding temperature) The cooling rate is controlled by the process) → rolling → correction / polishing / cleaning. According to this manufacturing method, by performing an intermediate solution treatment before rolling, precipitates can be made fine and minimal, and subsequent rolling can refine the structure and improve mechanical properties. .

(Production method 2)
On the other hand, when the magnesium alloy material of the present invention is a form formed by a manufacturing method that does not include a rolling process, typically a molded body (including irregularly shaped bodies) formed by die casting or the like, for example, the following preparation It can be produced by a production method comprising a process and a final solution treatment process.
Preparation step: A step of preparing one material selected from a die-cast material made of a magnesium alloy containing Al in a range of 7.3 mass% to 16 mass%, a thixo mold material, and an extruded material.
Final solution treatment step: Holding temperature in the above material: Mg-Al binary phase diagram (mass%) 10 ° C lower than the temperature at which Al dissolves in Mg (minimum holding temperature), holding time: 1 hour The step of applying a final solution treatment for 40 hours or less.
In particular, the cooling rate in the temperature range of 330 ° C. to 380 ° C. satisfies the following.
When a region from the surface of the material to 10 μm in the thickness direction is a surface layer region, the surface layer region is cooled at 1 ° C./min or more.

  In the production method 2, a specific Al concentration distribution that satisfies the above-mentioned conditions (1) to (3) by applying the final solution treatment similar to the production method 1-2 described above to the material prepared in the preparation step. It can be set as the solution material which has this. In particular, the production method 2 can be suitably used for producing a magnesium alloy material having a complicated three-dimensional shape as described above.

  Known conditions can be used as the die casting conditions and thixo mold conditions. The extruded material can be manufactured, for example, by preparing an ingot made of a magnesium alloy containing the specific amount of Al and extruding it under known conditions.

≪Other processes≫
(1) to (3) described above by providing a polishing step for polishing (preferably wet polishing) the rolled material, heat-treated material, straightening material, and solution-treated material obtained by the manufacturing methods 1 and 2. An abrasive having a specific Al concentration distribution that satisfies the above condition (one form of the magnesium alloy material of the present invention) is obtained. Further, in any of the manufacturing methods 1 and 2, the above-described (1) to (3) are further provided by including a step of performing an anticorrosion treatment such as a chemical conversion treatment or an anodizing treatment or a step of forming a coating layer. The magnesium alloy material of the present invention comprising a base material having a specific Al concentration distribution that satisfies the conditions (2) and an anticorrosion layer or coating layer formed on the base material is obtained. Known materials and conditions can be used for the material and forming conditions of the anticorrosion layer and the coating layer. In the anticorrosion treatment, pretreatment such as degreasing, acid etching, desmutting, and surface adjustment is preferably performed. In the case of performing plastic working, if the anticorrosion layer and the coating layer are formed after the plastic working, damage to the anticorrosion layer and the coating layer during the plastic working can be prevented.

Hereinafter, more specific embodiments of the present invention will be described.
[Test Example 1]
Magnesium alloy materials containing Al were prepared under various conditions, and the Al concentration distribution and corrosion resistance were investigated.

  In this test, a magnesium alloy material of Sample Nos. 1 to 5 prepared as follows and a commercially available die-cast material (AZ91 alloy, plate material having a thickness of 3 mm, a width of 75 mm, and a length of 150 mm) were prepared as a comparison. This die cast material was subjected to wet belt polishing under the same conditions as the polishing treatment applied to Samples Nos. 1 to 5 described later to produce a polishing plate. This polishing plate was designated as Sample No. 100.

The manufacturing process of sample No. 1-5 is shown below.
Sample No.1: Coil material (No final solution after rolling)
Casting → Intermediate solution → Rolling → Straightening → Polishing Sample No.2: Solution coil material (with final solution after rolling)
Casting-> Intermediate solution->Rolling-> Final solution->Correction-> Polishing Sample No.3: Sheet material (rapid heating / cooling material) * No winding
Casting (cutting after casting) → Intermediate solution → Rolling → Straightening → Polishing Sample No. 4: Solution material (die casting)
Preparation of die-cast material → final solution sample No. 5: solution material (extrusion)
Preparation of extruded material → final solution

<Sample No. 1, 2>
Long cast plate (thickness 4mm, width 300mm) made of a magnesium alloy with a composition equivalent to AZ91 alloy (Mg-8.75% Al-0.65% Zn (all mass%)) and obtained by twin-roll continuous casting method Was wound up once to produce a cast coil material. This cast coil material was charged into a batch heating furnace and subjected to a solution treatment (intermediate solution treatment) at 400 ° C. (≧ 20 × 8.75 + 172 = 347 ° C.) × 24 hours. The obtained intermediate solution coil material was rewound and rolled by multiple passes under the following conditions to produce a rolled coil material having a thickness of 0.6 mm, a width of 250 mm, and a length of 800 m.

(Rolling conditions)
Rolling rate: 5% / pass to 40% / pass Material temperature: 200 ° C to 280 ° C
Roll temperature: 100 ℃ ~ 250 ℃

  Here, the unwound material is passed between a feeding drum housed in a heating furnace and a take-up drum housed in another heating furnace, and the materials run between both drums by the rotation of both drums. I did it. Further, a rolling roll is disposed between these two drums so that the material to be rolled is rolled. Here, the feeding drum and the winding drum are rotated counterclockwise for each pass, and the feeding and winding are reversed to perform a plurality of passes of rolling continuously. And the raw material wound up by the heating furnace for every pass was heated so that it might become the said temperature, and the raw material of a heating state was made to drive between drums.

  After the final warm rolling pass is applied to the material, it is wound up as it is, and after adjusting the temperature of the material in the heating furnace, it is cooled by blowing wind adjusted to a certain temperature on the rewinded material. The speed was adjusted. Here, the average cooling rate until the temperature of the material (200 ° C to 280 ° C) reaches 100 ° C is as follows: Sample No. 1: 2.0 ° C / min, Sample No. 2: 1.7 ° C / min, 100 ° C to room temperature ( The temperature of the wind was adjusted and cooled so that the average cooling rate until it reached about 20 ° C. was Sample No. 1: 1.0 ° C./min and Sample No. 2: 0.9 ° C./min. And the rolled coil material was produced by winding up the rolled sheet returned to room temperature.

  The rolled coil material is rewound and warmed by a roll leveler device to produce a straightened coil material (material temperature: 250 ° C.). The straightened coil material is rewound and a # 600 polishing belt is used. Then, wet belt polishing was performed, and the obtained polishing plate was wound up to produce a polishing coil material. This polishing coil material is designated as sample No. 1. In sample No. 1, after the intermediate solution treatment, in the manufacturing process until the final polishing coil material is obtained, the total time for holding the material in the temperature range of 150 ° C. to 300 ° C. is within 12 hours, No heating above 300 ° C was performed.

  On the other hand, the rolled coil material was charged into a batch furnace and subjected to a final solution treatment at 350 ° C. (≧ (20 × 8.75 + 172) = 347) × 1 hour, and then forcedly cooled to room temperature (about 20 ° C.). Cooled down. Cooling was performed by blowing cold air to the cylindrical surface of the coil material taken out from the batch furnace by a jet ejection mechanism. In particular, the average cooling rate of the surface layer region (region from the surface to 10 μm in the thickness direction) of the plate material constituting the coil material in the temperature range of 380 ° C. to 330 ° C. is 3 ° C./min (≧ 1 ° C./min). The temperature, air volume, and wind speed of the cold air were adjusted so that Here, a thermocouple was attached to an appropriate position of the coil material, and the above adjustment was performed so that the cooling rate at the slowest cooling point was 3 ° C./min. In addition, although it cooled with the coil material here, you may cool in the state which wound the coil material.

  The obtained solution coil material was unwound and subjected to warm correction and wet belt polishing under the same conditions as in Sample No. 1. The obtained polishing coil material is designated as sample No. 2. In Sample No. 2, the total time for holding the material in the temperature range of 150 ° C to 300 ° C is within 12 hours in the manufacturing process after the final solution treatment until the final polished coil material is obtained. And heating above 300 ° C. was not performed. In sample No. 2, the process in which the material is held in the temperature range of 150 ° C. to 300 ° C. after the final solution treatment is substantially only warm correction. Here, since warm correction is performed on the material thinned by rolling, the holding time in the temperature range can be set to about several minutes.

<Sample No. 3>
A plurality of cast plates (a cast sheet material having a thickness of 5 mm, a width of 300 mm, and a length of 500 mm) made of a magnesium alloy having the same composition as Sample Nos. 1 and 2 and obtained by a twin roll continuous casting method were prepared. Each of the obtained cast plates was subjected to a solution treatment (intermediate solution treatment) at 400 ° C. for 24 hours, and then subjected to the same conditions as sample Nos. 1 and 2 while cutting to adjust the length. Then, a plurality of passes were rolled to produce a rolled plate (sheet material) having a thickness of 0.6 mm, a width of 300 mm, and a length of 2000 mm. Preheating was performed by a heating means capable of rapid heating before each rolling pass, and the material was heated to a predetermined temperature. The total holding time in the preheating is 3 hours. In addition, after the final warm rolling pass was applied to the material, the material was placed on a cooling steel plate (which can be controlled by circulating the heat medium) to adjust the cooling rate. Here, the average cooling rate until the temperature of the material (200 ° C to 280 ° C) reaches 100 ° C is 60 ° C / min, and the average cooling rate until it reaches room temperature (about 20 ° C) is 40 ° C / min. The steel sheet for cooling was cooled by adjusting the temperature and mounting time. The produced rolled plate was subjected to warm correction and wet belt polishing under the same conditions as in Sample Nos. 1 and 2. The obtained polishing plate (sheet material; hereinafter sometimes referred to as a rapid heating and quenching material) is designated as sample No. 3. Sample No. 3 is also the same as Sample No. 1, in the manufacturing process from the intermediate solution treatment until the final polishing plate is obtained, the total time for holding the material in the temperature range of 150 ° C to 300 ° C Was within 12 hours, and heating above 300 ° C. was not performed.

<Sample No. 4>
Prepare a commercially available die casting material (AZ91 alloy (Al: 8.75 mass%), thickness 3 mm, width 75 mm, length 150 mm) similar to sample No. 100, and use this die casting material at 380 ° C (≧ (20 × 8.75 + 172) = 347) × After 20 hours of final solution treatment, the solution was cooled to room temperature (about 20 ° C.) by forced cooling. This cooling is performed by spraying cold air on the surface of the plate material using a jet ejection mechanism in the same manner as Sample No. 2, and the cooling rate of the surface layer region in the temperature range of 380 ° C. to 330 ° C. is 50 ° C./min (≧ The temperature, air volume, wind speed, etc. of the cold air were adjusted so as to be 1 ° C / min. After the forced cooling, flattening (correction) was performed by warm pressing under conditions of 250 ° C. or lower, and then wet polishing was performed in the same manner as Sample Nos. 1 and 2. The obtained polishing plate is designated as sample No. 4.

<Sample No. 5>
After remelting and casting a commercially available die-cast material similar to sample No. 100, an extruded material (AZ91 alloy, thickness 3 mm, width 50 mm, length 150 mm) was prepared, and this extruded material was 380 ° C × After the final solution treatment for 20 hours, it was cooled by forced cooling to room temperature (about 20 ° C.) using a jet ejection mechanism in the same manner as in Sample No. 4. After this forced cooling, correction and wet polishing by warm pressing is performed under the same conditions as in Sample No. 4, and the resulting polishing plate is referred to as Sample No. 5. Sample No. 5 was also adjusted in temperature, air volume, and wind speed so that the cooling rate of the surface layer region in the temperature range of 380 ° C. to 330 ° C. was 50 ° C./min (≧ 1 ° C./min).

  The adjustment of the cooling rate in the cooling step after the final warm rolling and the cooling rate in the final solution treatment step can be easily performed by preparing the following correlation data in advance and referring to the correlation data. Enables temperature sensors to measure the temperature of the outermost surface to be cooled, such as multiple coil materials and sheet materials with different thickness, length, and number of turns, or a point 10 μm from the surface (for example, forming grooves at the above points) When the parameters of forced cooling means such as cold air temperature, air volume, and wind speed are appropriately changed, the temperature of the material at the start of cooling in the cooling process is changed to 100 ° C. The cooling rate is obtained by measuring the time to reach or the time from 380 ° C to 330 ° C, and the correlation data between each parameter and the cooling rate is created. When the object to be cooled is a coil material, a temperature sensor may be arranged at an appropriate position of the coil material, and correlation data relating to the cooling rate of the slowest cooling portion may be created in advance.

  From the obtained sample Nos. 1 to 5 and the comparative sample No. 100, the content of Al in the entire sample (Al total average amount): x In order to measure the mass%, a test piece for the total amount was cut out, and this When the total average amount of Al was determined by ICP emission spectroscopic analysis using the test piece, x was 8.75% by mass for all the samples.

  From the obtained sample Nos. 1 to 5 and the comparative sample No. 100, a test piece for mapping was cut out, and the analysis and measurement of the element: Al on the surface of each test piece was performed using an FE (Field Emission) -EPMA device ( JXA-8530F) manufactured by JEOL Ltd. was used. The measurement conditions are shown below.

(Measurement condition)
Acceleration voltage: 15kV
Irradiation current: 100nA
Sampling time: 50ms

  The content (mass%) of Al in the elemental analysis was determined by preparing the following calibration curve and converting the X-ray intensity of EPMA to the Al content (mass%) using this calibration curve.

(Create a calibration curve)
Commercially available AZ31 alloy materials, AZ61 alloy materials, and AZ91 alloy equivalent materials with different Al contents were subjected to solution treatment (400 ° C. × 120 hours) and homogenized to give samples. For the AZ91 alloy equivalent material, the solution coil material of Sample No. 2 was cut and used. Then, ICP emission spectroscopic analysis is performed on the surface of each sample, the Al content is measured, and elemental analysis is performed on FE-EPMA under the above measurement conditions, and the X-ray intensity (cps / μA) of Al is measured. To do.

Then, as shown in FIG. 4, the obtained X-ray intensity: y is expressed as a linear function of Al content: x, and an approximate expression of the linear function: y = 11977x + 1542.5 is used as a calibration curve. Note that this approximate expression is highly reliable with a correlation coefficient R ² of 0.9998.

  FIG. 1 is a mapping image (observation field: 24 μm × 18 μm) regarding the Al content obtained by analyzing the surface of each sample by FE-EPMA. Fig. 1 (A) is the coil material of sample No. 1, Fig. 1 (B) is the solution coil material of sample No. 2, Fig. 1 (C) is the sheet material of sample No. 3 (rapid quenching material), FIG. 1 (D) shows the die-cast material of sample No.100. Although shown in gray scale in FIG. 1, in practice, black (Al concentration: 0% by mass here) in descending order of Al content, depending on the Al concentration, 紺 to blue to light blue to green to yellow to orange -Red-Pink-White (Al concentration: 8.75 x 1.4 = 12.25% by mass or more). The white granule in FIGS. 1 (A), 1 (B), and 1 (C) and the white variant in FIG. 1 (D) are Al-rich intermetallic compounds.

  As shown in FIG. 1 (D), it can be seen that the die-cast material of sample No. 100 has many regions with a very high Al concentration. It can also be seen that there is a region where the Al concentration is very low. On the other hand, as shown in FIGS. 1 (A) to 1 (C), the coil material of sample No. 1, the solution coil material of sample No. 2, the sheet material of sample No. 3 (rapid heating and quenching) It can be seen that the material) does not have a large area where the Al concentration is very high. In particular, it can be seen that the solution coil material of sample No. 2 has a small and very small region where the Al concentration is very high. In addition, it can be seen that the coil material, the solution coil material, and the sheet material (rapid heating and quenching material) are substantially free of a region having a very low Al concentration. Sample Nos. 4 and 5 where the final solution treatment was applied to the die-cast material and extruded material, both in the same way as sample No. 2, the area where the Al concentration is very high is small and very low, and the Al concentration is very low. It was confirmed that there was substantially no low area.

  Using this mapping image, in the observation field of each sample, the area ratio of the low concentration region where the Al concentration is 4.2% by mass or less, and the Al concentration is 0.8x (= 8.75 × 0.8 = 7) mass% or more 1.2x (= 8.75) × 1.2 = 10.5) Area ratio of the central composition region of mass% or less, Al concentration of 0.9x (= 8.75 × 0.9 = 7.875) mass area of 1.2% by mass or less, Al concentration of 1.4x (= (8.75 × 1.4 = 12.25) The area ratio of the ultra-high concentration region of mass% or more, the maximum value and the minimum value of the Al concentration were obtained. The results are shown in Table 1. The Al concentration distribution is shown in the graph of FIG.

FIG. 3 is a scanning electron microscope (SEM) micrograph of each sample No. 1 to 3,100 (5000 times). The light gray granule in FIGS. 3 (A) to 3 (C) and the light gray variant in FIG. 3 (D) show precipitates. As shown in FIG. 3 (D), it can be seen that the die-cast material of sample No. 100 has large precipitates and an irregular shape. This is consistent with the fact that in the mapping image, the ultra-high concentration region having a very high Al concentration is large and has an irregular shape. In contrast, the coil material of sample No. 1 shown in FIG. 3 (A), the solution coil material of sample No. 2 shown in FIG. 3 (B), and the sheet of sample No. 3 shown in FIG. 3 (C) It can be seen that all the materials (rapid heating and quenching materials) have small precipitates, and all of them have a uniform circular granular body. In particular, the coil material of sample No. 1 has round particles of uniform size uniformly dispersed throughout, and the solution coil material of sample No. 2 has very high precipitates. It is very small and very small. This is consistent with the presence of small ultrahigh density regions in the mapping image. The solution material of Samples Nos. 4 and 5 had very small and very few precipitates, similar to the solution coil material of Sample No. 2. When the composition of the above-mentioned light gray particles and irregular shapes was examined with an EDS (Energy Dispersive X-ray Spectrometer), a metal containing Al or Mg such as Mg ₁₇ Al ₁₂ or Al (MnFe) It was an intermetallic compound. The presence of the intermetallic compound can also be determined by examining the composition and structure using X-ray diffraction or the like.

  The average particle diameter (μm) and the ratio (area%) of the total area of the intermetallic compounds of Sample Nos. 1 to 5,100 were measured. The results are also shown in Table 1. The average particle diameter and area ratio can be easily calculated by image processing the above micrograph using a commercially available image processing apparatus.

  The average particle size of the intermetallic compound was measured as follows. For each sample, five cross sections are taken in the thickness direction, and three fields of view (here, one field of view: 22.7 μm × 17 μm region) are arbitrarily taken from the observation image of each section. Here, the field of view was selected from the surface side region up to about 100 μm in the thickness direction from the surface of each sample. For each observation field, the equivalent circle diameter of each intermetallic compound existing in one observation field (the diameter of the equivalent area circle of the area of each intermetallic compound) is obtained, and the sum of the equivalent circle diameters is obtained as one observation field. A value obtained by dividing by the number of intermetallic compounds present therein: (total of equivalent circle diameter) / (total number) is defined as the average particle diameter of the observation visual field. Table 1 shows the average of the average particle diameters of 15 observation fields for each sample.

The ratio of the total area of the intermetallic compound was measured as follows. Take the observation field as described above, and for each observation field, calculate the total area by examining the area of all intermetallic compounds present in one observation field, this total area is the area of one observation field ( Here, the value divided by 385.9 μm ² ): (total area) / (area of observation field) is defined as the area ratio of the observation field. Table 1 shows the average of the area ratios of the 15 observation fields for each sample.

Each sample No. 1 to 5,100 was subjected to a salt water corrosion test, and the corrosion weight loss (μg / cm ² ) and Mg elution amount (μg / cm ² ) were measured. The results are shown in Table 1.

Corrosion weight loss was measured as follows by performing a salt spray test in accordance with JIS H 8502 (1999) as a salt water corrosion test. After preparing a test piece for corrosion from sample No. 1 to 5,100 and measuring the mass (initial value) of this test piece for corrosion, so that the test surface of a predetermined size is exposed in the test piece for corrosion, Mask unnecessary parts of the corrosion test piece. The masked corrosion test piece is inserted into the corrosion test apparatus and is placed so as to be inclined at a predetermined angle with respect to the apparatus bottom face (here, the angle formed by the apparatus bottom face and the test piece: 70 ° to 80 °). The test solution (5 mass% NaCl aqueous solution, temperature: 35 ± 2 ° C.) is sprayed on the corrosion test piece for a predetermined time (here 96 hours). After a predetermined time has elapsed, the corrosion test piece was taken out of the corrosion test apparatus, masking was removed, and the corrosion test piece was generated in accordance with the method described in Reference Table 1 of JIS Z 2371 (2000). Corrosion products are removed by chromic acid dissolution. The mass of the test piece for corrosion after removing the corrosion product is measured, and the value obtained by dividing the difference between the mass and the initial value by the area of the test surface of the test piece for corrosion is weight loss (μg / cm ² ). And

The amount of Mg elution was measured as follows by performing a salt water immersion test as a salt water corrosion test under the following conditions. A corrosion test piece is prepared from Sample Nos. 1 to 5,100, and unnecessary portions of the corrosion test piece are masked so that a test surface having a predetermined size is exposed in the corrosion test piece. Make the masked corrosion test piece into the test solution (5 mass% NaCl aqueous solution, liquid amount: (A) x 2 ml when the test piece area (exposed area) is (A) cm ² ) Hold for a predetermined time in a completely immersed state (here, hold for 96 hours at room temperature (25 ± 2 ° C.) under air conditioning). After a predetermined time has elapsed, the test solution is collected, the amount of Mg ions in the test solution is quantified with ICP-AES, and the value obtained by dividing the Mg ion amount by the area of the test surface of the corrosion test piece is the Mg elution amount ( μg / cm ² ).

  As shown in Table 1, in Sample Nos. 1 to 5, the central composition region having an Al concentration of 0.8x mass% to 1.2x mass% (here x = 8.75) in at least the surface side region has 50 area% or more. It can be seen that there is no low concentration region with an Al concentration of 4.2 mass% or less, and an ultrahigh concentration region with an Al concentration of 1.4 x mass% or more is 17.5 area% or less. In particular, sample Nos. 1 to 5 show that the ultra-high concentration region is 15 area% or less, and the region where the Al concentration is 0.9 × mass% to 1.2 × mass% is 30 area% or more. That is, it can be said that Sample Nos. 1 to 5 have small variations in Al concentration. This can also be seen from the graph in FIG. As shown in FIG. 2, it can be seen that all of the sample Nos. 1 to 3 have an Al concentration distribution in which the Al total average amount of each sample is 8.75 mass% and has a peak in the vicinity thereof. Moreover, sample No.1-3 show that the location where Al concentration is extremely low does not exist. Samples No. 4 and 5 also showed the same Al concentration distribution as Sample No. 2. And, as shown in Table 1, Sample Nos. 1 to 5 having a small variation in Al concentration have small corrosion weight loss and Mg elution amount, and are excellent in corrosion resistance.

  In particular, the solution composition coil material of sample No. 2, the sheet material of sample No. 3, and the solution material of sample Nos. 4 and 5 have a central composition region in which the Al concentration is 0.8x mass% to 1.2x mass%. It can be seen that, in addition to being very large at 70 area% or more, the ultra-high concentration region with an Al concentration of 1.4 x mass% or more is very small at 5 area% or less, and there are also samples with 3 area% or less. That is, it can be seen that Samples Nos. 2 to 5 have Al present more uniformly. In particular, Sample No. 2 has a very small ultra-high concentration region and a small difference between the maximum value and the minimum value of Al concentration, indicating that Al is present more uniformly. And it turns out that sample No. 2-5 which has such a uniform composition is excellent in corrosion resistance.

  In addition, the solution solution coil material of sample No. 2 and the solution solution materials of sample Nos. 4 and 5 that have undergone the final solution treatment have a low intermetallic compound of 3 area% or less and the maximum value of the Al concentration. It can be seen that it is relatively low. From this, it is considered that Samples Nos. 2, 4, and 5 are excellent in corrosion resistance. In particular, since sample No. 2 is a long material, it can contribute to mass production of a plastic processed material having excellent corrosion resistance, and is expected to have high industrial significance.

  On the other hand, the die-cast material of Sample No. 100 has a low concentration region where the Al concentration is 0.8x mass% to 1.2x mass% and the central composition region is small, and the Al concentration is 4.2 mass% or less. In particular, the minimum value of Al is equivalent to AZ31 alloy. From this, it can be considered that the sample No. 100 has a relatively inferior corrosion resistance, resulting in inferior corrosion resistance.

[Test Example 2]
After pressing the plate materials of Sample Nos. 1 to 5 prepared in Test Example 1, the Al concentration was measured in the same manner. Both the sample No. 1 coil material and the sample No. 2 solution coil material were unwound and cut to a predetermined length to produce a rectangular plate. Each of the prepared plate materials was preheated to 250 ° C. and subjected to press working in this heated state. The preheating holding time and the total time during pressing are 2 minutes (0.1 hour or less).

  All of the obtained press-worked materials (plastic work materials) had the same Al concentration distribution as Sample Nos. 1-5. From this, it is expected that these pressed materials are also excellent in corrosion resistance.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the composition of the magnesium alloy (particularly the Al content), the shape of the magnesium alloy material, the specifications (thickness, width, length), production conditions, etc. can be changed as appropriate.

  The magnesium alloy material of the present invention is a component member of various electric / electronic devices, particularly a portable or small-sized electric / electronic device casing, members of various fields where high strength is desired, for example, It can be suitably used for automobile parts and the like. Or this invention magnesium alloy material can be utilized suitably for the raw material of the said member.

Claims (5)

Magnesium alloy material composed of AZ91 alloy ,
The magnesium alloy material Ri sheet der,
When the content of Al in the entire magnesium alloy material is x mass%,
The area where the Al content is (x × 0.8) mass% or more and (x × 1.2) mass% or less is 50 area% or more,
The area where the Al content is (x × 1.4) mass% or more is 17.5 area% or less,
The region where the Al content is 4.2 mass% or less is not observed by EPMA measurement,
In the surface side region up 100μm in the thickness direction from the surface of the plate, includes at least one of Al and Mg, to dispersion average particle diameter of less intermetallic compound 3.0μm is divided,
A magnesium alloy material having a total area ratio of the intermetallic compounds of 11% or less .   2. The magnesium alloy material according to claim 1, wherein the magnesium alloy material is one of a coil material, a sheet material, and a plastic working material.   The magnesium alloy material according to claim 2, wherein the magnesium alloy material is a plastic work material, and the plastic work material is a press work material. The area where the Al content is (x × 0.8) mass% or more and (x × 1.2) mass% or less is 70 area% or more,
Al magnesium alloy material according to any one of claims 3 content is between (x × 1.4) according to claim 1 mass% or more regions is 5 area% or less. The magnesium alloy material according to claim 3 or 4 , which has a through hole.