JP7329966B2 - Aluminum alloy material - Google Patents

Description

The present invention relates to an aluminum alloy material.

2. Description of the Related Art In various fields such as industrial products, buildings, and structures, vibrations generated during use of equipment and vibrations applied from the outside may cause various problems. For example, in transportation equipment such as automobiles and railroads, there is a risk that the comfort of the passengers may deteriorate due to the vibration itself and the noise generated by the vibration. 2. Description of the Related Art In home electric appliances and audio equipment, noise generated by vibration may cause discomfort to users. In addition, for example, in precision equipment, there is a possibility that the operation of the equipment may be hindered by vibration.

In order to suppress the occurrence of these problems, various techniques for damping vibration have been proposed. For example, in the field of buildings and structures, a method of incorporating a damping member such as a damper, and a method of adopting a member having a shape that facilitates damping vibration as a member constituting a building or the like are frequently used. However, the method of incorporating the damping member may lead to an increase in the number of members such as industrial products. In addition, it is difficult to apply the method of attenuating vibration by the shape of the member to transportation equipment, home electric appliances, precision equipment, etc., where the size, mass, and shape of the member are greatly restricted.

In order to solve this problem, methods of assembling industrial products and the like using members made of aluminum alloys with high damping properties are being studied, taking advantage of the characteristics of aluminum alloys, which are relatively light weight and excellent in workability. For example, Patent Literature 1 describes an aluminum alloy damping material in which an aluminum alloy ingot containing Fe: 0.5 to 20 wt%, the balance being Al and unavoidable impurities is subjected to plastic working at a reduction of area of 30% or more. A manufacturing method is described.

JP-A-3-223446

In recent years, an aluminum alloy material with higher damping properties than the aluminum alloy damping material of Patent Document 1 has been demanded.

The present invention has been made in view of such a background, and an object thereof is to provide an aluminum alloy material having high damping properties.

One aspect of the present invention is
An aluminum alloy material having an Al matrix and second phase particles dispersed in the Al matrix,
The aluminum alloy material has a chemical composition containing 0.30 to 3.0% by mass of Fe, with the balance being Al and unavoidable impurities,
An aluminum alloy material having a value of a metal structure factor F represented by the following formula (1) of 0.005 or more.
F=A・ρ・L・exp(B・E) (1)

However, L in the above formula (1) is the total circumference length [μm/μm ² ] of the second phase particles having an equivalent circle diameter of 0.2 μm or more among the second phase particles existing in an arbitrary cross section, and ρ is the dislocation density [μm ⁻² ], E is the electrical conductivity [%IACS] at 25° C., and A and B are correction coefficients determined according to the chemical composition of the aluminum alloy material. A and B can take values within the ranges of 0.2×10 ⁻¹⁵ ≦A≦20×10 ⁻¹⁵ and 0.1≦B≦1.0, respectively.

In the aluminum alloy material, the value of the metallographic factor F represented by the total circumferential length L of the second phase particles having an equivalent circle diameter of 2 μm or more, the dislocation density ρ, and the electrical conductivity E is within the specific range. As a result, the interaction between the second-phase particles and the dislocations in the Al matrix can efficiently attenuate the vibration applied from the outside of the aluminum alloy material. As a result, it is possible to improve the damping property more than the conventional aluminum alloy material.

Therefore, according to the aspect, it is possible to provide an aluminum alloy material having excellent damping properties.

It is an example of a backscattered electron image of an L-LT cross section of an aluminum alloy material in an example. It is an example of a binarized image obtained by subjecting the backscattered electron image of FIG. 1 to binarization processing. FIG. 2 is a side view showing a main part of a loss factor measuring device in an example. FIG. 4 is an explanatory diagram showing an example of an amplitude-frequency curve in an example;

(Chemical composition)
The aluminum alloy material contains Al (aluminum) and one or more additive elements for forming second phase particles in the Al matrix. Examples of additive elements include Fe (iron), Mn (manganese), Si (silicon), Cu (copper), Mg (magnesium), Zn (zinc), Ni (nickel), Cr (chromium), Ti (titanium ), V (vanadium), Zr (zirconium) and the like can be used. By adding these additive elements to the aluminum alloy, second phase particles containing the additive elements can be formed in the Al matrix.

・ Fe (iron): 0.30 to 3.0% by mass
The aluminum alloy material contains 0.30 to 3.0% by mass of Fe. By setting the Fe content to 0.30% by mass or more, the amount of second phase particles in the Al matrix can be increased, and the damping properties of the aluminum alloy material can be improved. From the viewpoint of further improving the damping properties of the aluminum alloy material, the Fe content is preferably 0.50% by mass or more.

On the other hand, when the Fe content is excessively high, coarse second phase particles are likely to be formed in the aluminum alloy material, which may lead to deterioration in rollability. By setting the Fe content to 3.0% by mass or less, preferably 2.0% by mass or less, it is possible to easily avoid such problems and improve the damping properties of the aluminum alloy material.

・Mn: 0.10 to 1.50% by mass
The aluminum alloy material may contain 0.10 to 1.50% by mass of Mn. By setting the Mn content to 0.10% by mass or more, the amount of second phase particles in the Al matrix can be increased, and the damping properties of the aluminum alloy material can be further improved. From the viewpoint of further improving the damping properties of the aluminum alloy material, it is more preferable to set the Mn content to 0.20% by mass or more.

On the other hand, if the Mn content is excessively high, coarse second phase particles are likely to be formed in the aluminum alloy material, which may lead to deterioration in rollability. From the viewpoint of easily avoiding such problems and obtaining the effect of improving damping properties, the Mn content is preferably 1.50% by mass or less, more preferably 1.0% by mass or less.

・Si: 0.0050 to 3.0% by mass
The aluminum alloy material may contain 0.0050 to 3.0% by mass of Si. By setting the Si content to 0.0050% by mass or more, the amount of second phase particles in the Al matrix can be increased, and the damping properties of the aluminum alloy material can be further improved. From the viewpoint of further improving the damping properties of the aluminum alloy material, it is more preferable to set the Si content to 0.050% by mass or more.

On the other hand, if the Si content is excessively high, coarse second phase particles are likely to be formed in the aluminum alloy material, which may lead to deterioration in rollability. Moreover, in this case, the amount of the additive element solid-soluted in the Al matrix increases, which may lead to a decrease in damping performance. From the viewpoint of avoiding such problems and obtaining the effect of improving damping properties, the Si content is preferably 3.0% by mass or less, more preferably 2.0% by mass or less.

・Cu: 0.0030 to 0.10% by mass
The aluminum alloy material may contain 0.0030 to 0.10% by mass of Cu. By setting the Cu content to 0.0030% by mass or more, the amount of second phase particles in the Al matrix can be increased, and the damping properties of the aluminum alloy material can be further improved. From the viewpoint of further improving the damping properties of the aluminum alloy material, it is more preferable to set the Cu content to 0.010% by mass or more.

On the other hand, when the Cu content is excessively high, coarse second phase particles are likely to be formed in the aluminum alloy material, which may lead to deterioration in rollability. Moreover, in this case, the amount of the additive element solid-soluted in the Al matrix increases, which may lead to a decrease in damping performance. From the viewpoint of easily avoiding such a problem and obtaining the effect of improving the damping property, the Cu content is preferably 0.10% by mass or less, more preferably 0.050% by mass or less.

・Mg: 0.0050 to 3.0% by mass
The aluminum alloy material may contain 0.0050 to 3.0% by mass of Mg. By setting the Mg content to 0.0050% by mass or more, the amount of second phase particles in the Al matrix can be increased, and the damping properties of the aluminum alloy material can be further improved. From the viewpoint of further improving the damping properties of the aluminum alloy material, it is more preferable to set the Mg content to 0.050% by mass or more.

On the other hand, when the content of Mg is excessively high, the amount of additive elements solid-soluted in the Al matrix increases, which may lead to deterioration of damping properties. From the viewpoint of avoiding such a problem and obtaining the effect of improving damping properties, the content of Mg is preferably 3.0% by mass or less, more preferably 1.50% by mass or less.

・Zn: 0.10 to 0.50% by mass
The aluminum alloy material may contain 0.10 to 0.50% by mass of Zn. By setting the Zn content to 0.10% by mass or more, the amount of second phase particles in the Al matrix can be increased, and the damping properties of the aluminum alloy material can be further improved. From the viewpoint of further improving the damping properties of the aluminum alloy material, it is more preferable to set the Zn content to 0.20% by mass or more.

On the other hand, if the Zn content is excessively high, the amount of additive elements solid-soluted in the Al matrix increases, which may lead to a decrease in damping properties. From the viewpoint of easily avoiding such a problem and obtaining the effect of improving damping properties, the Zn content is preferably 0.50% by mass or less, more preferably 0.40% by mass or less.

・Ni: 0.050 to 0.30% by mass, Cr: 0.050 to 0.30% by mass, Ti: 0.050 to 0.30% by mass, V: 0.050 to 0.30% by mass
The aluminum alloy material contains Ni: 0.050 to 0.30 mass%, Cr: 0.050 to 0.30 mass%, Ti: 0.050 to 0.30 mass%, V: 0.050 to 0.30 mass%. It may contain one or more of 30% by mass. By setting the content of these additive elements to 0.050% by mass or more, the damping properties of the aluminum alloy material can be further improved. From the viewpoint of further improving the damping properties of the aluminum alloy material, it is more preferable to set the content of these additive elements to 0.10% by mass or more.

On the other hand, if the content of these additive elements is excessively large, coarse second phase particles are likely to be formed in the aluminum alloy material, which may lead to deterioration of rollability. From the viewpoint of obtaining the effect of improving the damping property while avoiding such problems, the content of these additive elements is preferably 0.30% by mass or less, more preferably 0.20% by mass or less. .

・ Zr: 0.0010 to 0.30% by mass
The aluminum alloy material may contain 0.0010 to 0.30% by mass of Zr. By setting the Zr content to 0.0010% by mass or more, the damping property of the aluminum alloy material can be further improved. From the viewpoint of further improving the damping properties of the aluminum alloy material, it is more preferable to set the Zr content to 0.010% by mass or more.

On the other hand, when the Zr content is excessively large, coarse second phase particles are likely to be formed in the aluminum alloy material, which may lead to deterioration in rollability. From the viewpoint of obtaining the effect of improving the damping property while avoiding such a problem, the Zr content is preferably 0.30% by mass or less, more preferably 0.20% by mass or less.

[Metal structure]
The aluminum alloy material has second phase particles dispersed in an Al matrix. The second phase particles are, for example, Al--Fe-based compounds, Si, Al--Fe--Mn-based compounds, Al--Fe--Si-based compounds, Al--Mn-based compounds, Al--Mn--Si-based compounds, Al--Fe-- Mn-Si compounds, Al-Cu compounds, Al-Mg compounds, Mg-Si compounds, Al-Mg-Zn compounds, Al-Cu-Zn compounds, Al-Ni compounds, Al-Cr compounds compound, Al--Ti based compound, Al--V based compound, Al--Zr based compound and the like. The second phase particles may be precipitates or crystallized substances.

The second phase particles dispersed in the Al matrix have various particle sizes. In addition to second-phase particles having an equivalent circle diameter of 0.2 μm or more, the aluminum alloy material may contain second-phase particles having an equivalent circle diameter of less than 0.2 μm. Second phase particles less than 2 μm may not be included. If the aluminum alloy material has second-phase particles having an equivalent circle diameter of 0.2 μm or more in the Al matrix, it is possible to obtain the effect of improving the damping property.

Moreover, as described above, when coarse second phase particles are formed in the Al matrix, there is a risk of deterioration in rollability. From the viewpoint of easily avoiding such problems, the equivalent circle diameter of the second phase particles dispersed in the Al matrix is preferably 20 μm or less.

[Metal structure factor F]
As described above, the aluminum alloy material can reduce vibration due to the interaction between the second phase particles dispersed in the Al matrix and the dislocations. Therefore, in order to improve the damping property of the aluminum alloy material, it is necessary to control not only the aspect of the second phase particles in the metal structure but also the aspect of the dislocations. The characteristics of the metallographic structure related to the damping property of the aluminum alloy material can be represented by the value of the metallographic structure factor F shown in the following formula (1).
F=A・ρ・L・exp(B・E) (1)

However, the symbol L in the formula (1) is the total circumference length [μm/μm ² ] of the second phase particles having an equivalent circle diameter of 0.2 μm or more among the second phase particles existing in an arbitrary cross section, The symbol ρ is the dislocation density [μm ⁻² ], the symbol E is the electrical conductivity [%IACS] at 25° C., and the symbols A and B are correction coefficients determined according to the chemical composition of the aluminum alloy material.

In a metallographic structure having a metallographic factor F of 0.005 or more, the form of existence of additive elements contained in the aluminum alloy material and the form of existence of dislocations in the matrix are important factors for damping vibration. It tends to be in a suitable form. Therefore, an aluminum alloy material having a value of metallographic factor F of 0.005 or more can improve damping properties. From the viewpoint of further improving the damping property, the value of the metal structure factor F is preferably 0.01 or more, more preferably 0.05 or more. Although there is no upper limit to the value of the metallographic factor F from the viewpoint of improving damping properties, it is difficult to obtain an aluminum alloy material with a value of the metallographic factor F exceeding 400 by a general manufacturing method.

When the value of the metallographic structure factor F is less than 0.005, the effect of lowering the damping property due to the solid solution element tends to exceed the effect of improving the damping property due to the interaction between the second phase particles and the dislocations. There is a risk of causing a decrease in damping performance.

Individual parameters used to calculate the value of the metallographic factor F can be determined as follows.

・ Peripheral length L of second phase particles

The total circumference L of the second phase particles having an equivalent circle diameter of 0.2 μm or more can be calculated by the following method. First, using a scanning electron microscope, a cross section of the aluminum alloy material is observed to obtain a backscattered electron image. The magnification during observation can be appropriately set, for example, within the range of 1000 to 5000 times.

The cross section to be observed is not particularly limited. For example, when the aluminum alloy material is a rolled plate, the cross section to be observed may be the LT-ST plane (that is, the cross section perpendicular to the rolling direction) or the L-LT plane (that is, the plate surface ) or the L-ST plane (that is, a cross section parallel to the rolling direction). When the aluminum alloy material is an extruded material, the cross section to be observed may be a cross section parallel to the extrusion direction or a cross section perpendicular to the extrusion direction. Furthermore, the cross section to be observed may be a cross section other than these.

Next, the backscattered electron image is binarized using an image processing device or the like to obtain a binarized image in which the Al matrix and the second phase particles are shown with different brightness. Second phase particles having an equivalent circle diameter of 0.2 μm or more are extracted from this binarized image, and the peripheral length of these second phase particles is calculated. Then, the total peripheral length of the second phase particles having an equivalent circle diameter of 0.2 μm or more present in the binarized image is converted into a value per 1 μm ² of area. The value obtained as described above is defined as the total value L [μm/μm ² ] of the peripheral length of the second phase particles having an equivalent circle diameter of 0.2 μm or more.

The total peripheral length L of the second phase particles is preferably 0.1 μm/μm ² or more, more preferably 0.2 μm/μm ² or more. By increasing the total perimeter L of the second phase grains, the interaction between the second phase grains and the dislocations can be made stronger. As a result, the damping property of the aluminum alloy material can be further improved. From the viewpoint of improving damping properties, there is no upper limit to the total peripheral length, but in a general manufacturing method, an aluminum alloy material in which the total peripheral length L exceeds 3.0 μm/μm ² is obtained. It is difficult.

・Dislocation density ρ
The dislocation density ρ in an aluminum alloy material can be measured by the following method. First, diffraction profiles are obtained for a plurality of aluminum alloy materials by the X-ray diffraction method. Next, the peak position 2θ of the peaks present in the diffraction profile and the integrated width β of each peak (that is, the full width of the peak) are read.

Next, based on the Williamson-Hall formula (formula (2) below), the value of the non-uniform strain h of the aluminum alloy material is calculated from the value of the peak position 2θ and the value of the integral width β. Note that λ in the following formula (2) is a symbol indicating the wavelength of incident X-rays, and D is a symbol indicating the size of crystallites.

As shown in the above formula (2), the value of the nonuniform strain h is obtained by multiplying the slope of a straight line with the value of β cos θ/λ on the vertical axis and the value of sin θ/λ on the horizontal axis by 1/2. equal to the value Therefore, first, for all peaks present in the diffraction profile, data points are plotted in the graph so that the value on the vertical axis is β cos θ / λ, and the value on the horizontal axis is sin θ / λ, and a Williamson-Hall plot is created. create. A straight line fit to these data points is then determined by the method of least squares. By multiplying the slope of this approximate straight line by 1/2, the value of non-uniform strain h can be calculated.

For example, when the crystal grains of the aluminum alloy material are coarse, the intensity of the peak associated with a specific crystal orientation in the diffraction profile may be extremely low. In this case, the integrated width of the peak is strongly affected by the background, and some data points may appear as abnormal values in the Williamson-Hall plot. In this case, after removing the data point from the Williamson-Hall plot, the measurement position is changed for the aluminum alloy material from which the data point was obtained, and the diffraction profile is obtained again. - Add data points to the Hall plot.

The value of dislocation density ρ can be calculated by substituting the value of non-uniform strain h into the following equation (3). Note that b in the following formula (3) is a symbol indicating the Burgers vector of aluminum. The value of b is specifically 0.2863 nm.

The dislocation density ρ of the aluminum alloy material is preferably 10 μm ⁻² or more, more preferably 20 μm ⁻² or more, and even more preferably 50 μm ⁻² or more. By increasing the dislocation density ρ, the interaction between the second phase grains and the dislocations can be made stronger. As a result, the damping property of the aluminum alloy material can be further improved. Although there is no upper limit to the dislocation density ρ of the aluminum alloy material from the viewpoint of improving damping properties, it is difficult to obtain an aluminum alloy material having a dislocation density exceeding 2000 μm ⁻² by a general manufacturing method.

・Conductivity E
The conductivity E of the aluminum alloy material at 25° C. is 50% IACS or more. The electrical conductivity E of the aluminum alloy material increases as the additive element precipitates or crystallizes as second-phase particles and the amount of the additive element dissolved in the Al matrix decreases. By setting the electrical conductivity E of the aluminum alloy material to 50% IACS or more, the amount of solid-solution additive elements that hinder dislocation movement can be reduced. As a result, the effect of improving the damping property by the interaction between the dislocations and the second phase particles can be further enhanced. From the viewpoint of further improving the damping property, it is more preferable that the conductivity of the aluminum alloy material at 25° C. is 55%IACS or more.

If the electrical conductivity E is less than 50% IACS, the dislocation movement is likely to be inhibited by the additive element dissolved in the Al matrix. As a result, interaction between the dislocations and the second phase grains becomes difficult to occur, which may lead to deterioration of the damping properties.

Although there is no upper limit to the value of the conductivity E from the viewpoint of enhancing the damping property, the value of the conductivity is 64%IACS or less due to the physical properties of the aluminum alloy.

・Correction coefficients A and B
The correction coefficient A and the correction coefficient B in the metallographic factors can take various values according to the type and amount of additive elements contained in the aluminum alloy material. The reason for this is, for example, that when the type and amount of the additive element changes, the phase that constitutes the second phase particles changes, and the contribution of the interaction between the second phase particles and the dislocation changes. It is conceivable that the degree of inhibition of dislocation movement by the additive element solid-soluted in the Al matrix changes when the type and amount change.

Specifically, the range of the value of the correction coefficient A is 0.2×10 ⁻¹⁵ ≦A≦20×10 ⁻¹⁵ , and the range of the value of the correction coefficient B is 0.1≦B≦1.0. be. Among multiple types of aluminum alloy materials with different types and amounts of additive elements, the same correction factor A and correction factor B values are used for aluminum alloy materials with the same type of additive element with the highest content. be able to. For example, when the aluminum alloy material contains 0.3 to 3.0% by mass of Fe as the additive element with the highest content, the value of A is 2.0 × 10 ^-15 , and the value of B is 0.4851 can be used as

The values of correction coefficient A and correction coefficient B can be determined by the following method. First, a plurality of types of aluminum alloy materials having the same type of additive element with the highest content and different contents of the additive element, content of other additive elements, manufacturing conditions, etc. are prepared. Then, the total perimeter length L, dislocation density ρ, and electrical conductivity E of these aluminum alloy materials are calculated. By approximating the plot created using these values with the above equation (1), the values of the correction coefficients A and B can be determined.

[Damping property]
The damping property of the aluminum alloy material is based on the corrected loss coefficient η _c (see formula (4) below) obtained by correcting the loss coefficient η measured by the free resonance method according to the sample shape of the aluminum alloy material. can be evaluated as
_ηc = η - 0.556 x t ^-2.434 + 1.5 (4)

The symbol t in the formula (4) is the thickness [mm] of the test piece used for measuring the loss factor η. The length of the test piece used for measuring the loss factor η is 60 mm and the width is 8 mm.

The corrected loss factor η _c is preferably 1.6×10 ⁻³ or more, more preferably 1.8×10 ⁻³ or more, and even more preferably 2.0×10 ⁻³ or more. In this case, the damping property of the aluminum alloy material can be further improved. Although there is no upper limit to the corrected loss factor η _c from the viewpoint of improving damping properties, the corrected loss factor η _c is usually 300×10 ^{− 3} or less.

In addition to the free resonance method, there are other methods for measuring the loss factor, such as the cantilever vibration method. However, as a result of intensive studies by the present inventors, in the cantilever vibration method, the value of the loss factor may vary depending on the shape of the test piece. It was clarified that when the length of the test piece is long, the value of the loss factor tends to be larger than when the length of the test piece is short, although the chemical composition and metallographic structure are the same. Therefore, it is not possible to simply compare the loss factor value obtained by the cantilever vibration method and the loss factor value obtained by the free resonance method.

Further, as a result of the inventors' earnest studies, it has become clear that even in the free resonance method, the value of the loss factor changes according to the thickness and area of the test piece. The reason for this is thought to be friction between the test piece and air during measurement. Therefore, the value of the loss factor obtained by the free resonance method cannot be simply compared with the value of the corrected loss factor.

-Crystal Grain The aluminum alloy material preferably contains a fibrous structure, and more preferably consists of a fibrous structure. In this case, the damping property of the aluminum alloy material can be further improved.

The fibrous structure refers to a structure having a large number of crystal grains elongated in the processing direction by stretching such as rolling, extrusion, or forging. The fibrous texture is observed as streaky patterns extending in the processing direction when a cross section parallel to the processing direction is observed using a metallographic microscope with a magnification of 25 to 100, for example. An equiaxed structure refers to a structure having a large number of equiaxed crystal grains. The equiaxed structure is observed as a granular pattern with a relatively small difference between the major axis and the minor axis when a cross section parallel to the processing direction is observed using a metallurgical microscope with a magnification of 25 to 100 times.

For the aluminum alloy material, for example, after casting an ingot having the specific chemical composition, depending on the casting method, the ingot is subjected to stretching such as rolling, extrusion, forging, etc., and heat treatment in combination as appropriate. It can be produced by

For example, as one aspect of the manufacturing method, a method of casting a slab as an ingot by a DC casting method and then successively subjecting the slab to hot rolling and cold rolling as stretching can be adopted.

The casting speed in DC casting is preferably within the range of 20-100 mm/min. By setting the casting speed within the specific range, the formation of coarse second phase particles can be suppressed.

In this embodiment, after DC casting, the slab may be heated and homogenized before hot rolling, or hot rolling may be performed without homogenizing. When the homogenization treatment is performed, the heating temperature can be appropriately set within a range of, for example, 200 to 550.degree. The heating temperature in the homogenization treatment is preferably 500° C. or lower, more preferably 340° C. or lower. In this case, the second phase particles in the Al matrix can be made finer and the peripheral length of the second phase particles can be increased. As a result, the interaction between the dislocations and the second phase particles can further improve the damping properties.

In the homogenization treatment, the heating may be terminated immediately after the temperature of the slab reaches the heating temperature, or the heating temperature may be maintained for a certain period of time. The holding time in the latter case can be 50 hours or less.

If the heating temperature in the homogenization treatment is less than 200°C, the slab may not be sufficiently homogenized. In addition, when the heating temperature in the homogenization treatment exceeds 550 ° C. or the holding time exceeds 50 hours, coarse second phase particles are likely to be formed in the slab, which may lead to a decrease in damping properties. be.

Next, the slab is hot-rolled to produce a hot-rolled sheet. The temperature of the slab at the start of hot rolling is preferably 200 to 550°C. If the temperature of the slab at the start of rolling is less than 200° C., the slab is difficult to deform, making it difficult to perform hot rolling. If the temperature of the slab at the start of rolling exceeds 550°C, coarse second phase particles are likely to be formed in the slab, which may lead to deterioration of damping properties.

The hot rolling may be performed while the temperature of the slab after casting is within the specific range. When the temperature of the slab after casting is lower than the specific temperature, the temperature of the slab can be brought to the specific range by heating the slab before hot rolling.

When the slab is heated before hot rolling, the heating may be terminated immediately after the temperature of the slab reaches the desired temperature, or the desired temperature may be maintained for a certain period of time. The holding time in the latter case can be 30 hours or less. When the holding time exceeds 30 hours, coarse second phase particles are likely to be formed in the slab, which may lead to deterioration of damping properties.

In this aspect, the hot-rolled sheet may be heated and annealed after hot-rolling and before cold-rolling. The heating temperature in this annealing can be appropriately set within the range of 200 to 400.degree. If the heating temperature in annealing is less than 200°C, the effect of intermediate annealing may be insufficient. If the heating temperature in the annealing exceeds 400°C, coarse second phase particles are likely to be formed in the hot-rolled sheet, which may lead to deterioration of damping properties.

In the annealing, heating may be terminated immediately after reaching the heating temperature, or the heating temperature may be maintained for a certain period of time. The holding time in the latter case can be 10 hours or less. When the holding time exceeds 10 hours, coarse second phase particles are likely to be formed in the hot-rolled sheet, which may lead to deterioration of damping properties.

After that, the hot-rolled sheet is subjected to one or more passes of cold rolling, whereby the aluminum alloy material can be obtained. In cold rolling, it is preferable to perform rolling so that the total rolling reduction is 50% or more. That is, the difference between the thickness of the hot-rolled sheet before cold rolling after hot rolling and the desired thickness of the aluminum alloy material is preferably 50% or more of the thickness of the hot-rolled sheet. . Thereby, the dislocation density of the aluminum alloy material can be further increased, and the damping property of the aluminum alloy material can be further improved.

When the number of cold rolling passes is two or more, intermediate annealing can be performed by heating the hot-rolled sheet between the cold rolling passes. The heating temperature in the intermediate annealing can be appropriately set within the range of 200 to 400.degree. If the heating temperature in the intermediate annealing is less than 200°C, the effect of the intermediate annealing may be insufficient. If the heating temperature in the intermediate annealing exceeds 400° C., coarse second phase particles are likely to be formed in the aluminum alloy material, which may lead to deterioration of damping properties.

Moreover, in the intermediate annealing, the heating may be terminated immediately after reaching the heating temperature, or the heating temperature may be maintained for a certain period of time. The holding time in the latter case can be 10 hours or less. If the holding time exceeds 10 hours, coarse second phase particles are likely to be formed in the aluminum alloy material, which may lead to deterioration of damping properties.

When the intermediate annealing is performed, it is preferable to perform rolling so that the rolling reduction after the intermediate annealing is 50% or more. That is, the difference between the thickness of the hot-rolled sheet before resuming cold rolling after performing intermediate annealing and the desired thickness of the aluminum alloy material is 50% of the thickness of the hot-rolled sheet before resuming cold rolling. % or more. Thereby, the dislocation density of the aluminum alloy material can be increased, and the damping property of the aluminum alloy material can be improved.

In this aspect, the final annealing may be performed by heating the aluminum alloy material after cold rolling. The heating temperature in the final annealing can be appropriately set within the range of 100 to 200°C. If the heating temperature in the final annealing is less than 100°C, the effect of final annealing may be insufficient. If the heating temperature in the final annealing exceeds 200° C., the dislocation density may be greatly reduced due to the rearrangement or disappearance of dislocations, resulting in deterioration of damping properties.

In the final annealing, the heating may be terminated immediately after reaching the heating temperature, or the heating temperature may be maintained for a certain period of time. The holding time in the latter case can be 10 hours or less. If the holding time exceeds 10 hours, the dislocation density may decrease due to the rearrangement or disappearance of the dislocations, resulting in deterioration of the damping properties.

As another aspect of the method for producing the aluminum alloy material, after casting a strip as an ingot by a continuous casting method such as a twin-roll continuous casting-rolling method or a twin-belt continuous casting method, the strip is stretched. A method of cold rolling can also be employed.

The casting speed in continuous casting is preferably in the range of 500-3000 mm/min. By setting the casting speed within the specific range, the formation of coarse second phase particles can be suppressed.

After continuous casting, the aluminum alloy material can be obtained by subjecting the strip to one or more passes of cold rolling. In the cold rolling, it is preferable to perform the rolling so that the total rolling reduction is 50% or more, similarly to the processing conditions for DC casting described above. In other words, the difference between the thickness of the strip before cold rolling after continuous casting and the desired thickness of the aluminum alloy material is preferably 50% or more of the thickness of the strip. Thereby, the dislocation density of the aluminum alloy material can be further increased, and the damping property of the aluminum alloy material can be further improved.

Also in this aspect, as in the case of DC casting described above, intermediate annealing may be performed between passes of cold rolling, or final annealing may be performed after cold rolling is completed. The processing conditions for the intermediate annealing and the processing conditions for the final annealing in this embodiment and the effects thereof are the same as the processing conditions for DC casting described above.

Examples of the aluminum alloy material will be described with reference to FIGS. 1 to 4. FIG. It should be noted that specific aspects of the aluminum alloy material according to the present invention are not limited to the aspects of the examples shown below, and the configuration can be appropriately changed from the examples within the scope that does not impair the gist of the present invention. be able to.

The aluminum alloy material according to this example can be produced by the following method. First, an ingot having the chemical composition shown in Table 1 is cast by the DC casting method. After heating this ingot at the heating temperature shown in the "heating before hot rolling" column of Table 1, hot rolling is performed to produce a hot-rolled sheet having a thickness shown in Table 1. The obtained hot-rolled sheet is cold-rolled so that the total rolling reduction becomes the value shown in Table 1. As described above, test materials 1 to 12 with a thickness of 0.75 mm and test materials 13 to 14 with a thickness of 2.0 mm shown in Table 1 can be obtained. In addition, since the test materials 15 and 16 shown in Table 1 have an excessively high content of Fe or Mn in the ingot, coarse second phase particles are likely to be formed. Therefore, it is difficult to roll these test materials.

The method for calculating the value of the metallographic structure factor F, the method for calculating the corrected loss factor _ηc , and the method for evaluating the morphology of crystal grains in these test materials are as follows.

[Calculation method of metal structure factor F]
The value of the metallographic structure factor F is the sum of the perimeters L [μm/μm ² ] of the second phase particles having an equivalent circle diameter of 0.2 μm or more, the dislocation density ρ [μm ⁻² ], and the conductivity It can be calculated by substituting the value of the rate E [IACS%] into the following formula (1). Note that the value of the correction coefficient A in this example is 2.0×10 ⁻¹⁵ and the value of the correction coefficient B is 0.4851. Table 2 shows the values of the metallographic factor F of the test material.
F=A・ρ・L・exp(B・E) (1)

Methods for measuring the values of L, ρ and E are detailed below.

・The total length L of the circumference of the second phase particles with an equivalent circle diameter of 0.2 μm or more
First, the plate surface of the test material is polished to expose the L-LT surface (surface parallel to the plate surface). A scanning electron microscope is used to observe five randomly selected observation positions from the L-LT surface to obtain backscattered electron images at a magnification of 2000 times. In the backscattered electron image, the Al matrix and the second phase particles dispersed in the Al matrix are displayed with different brightnesses. For example, in FIG. 1, the second phase particles 12 in the aluminum alloy material 1 are displayed with a brighter brightness than the Al matrix 11 .

Next, the backscattered electron image is binarized using an image processing device or the like to create a binarized image shown in FIG. In FIG. 2, for the sake of convenience, an inversion process for interchanging white and black is performed after creating the binarization process. The threshold in the binarization process may be appropriately set so that the outline of the second phase particles 12 in the backscattered electron image is maintained even after the binarization process.

After extracting the second phase particles 12 having an equivalent circle diameter of 0.2 μm or more from this binarized image, the peripheral length of each second phase particle 12 (that is, the length of the outline of the second phase particle 12) is measured. do. By dividing the total of these peripheral lengths by the total visual field area, the total peripheral length L [μm/μm ² ] of the second phase particles 12 having an equivalent circle diameter of 0.2 μm or more shown in Table 2 can be calculated. can be done.

・Dislocation density ρ
First, an X-ray diffraction profile of a test material is obtained using an X-ray diffraction device. The conditions for X-ray diffraction are as follows.
Measuring device: "Smart-labo (registered trademark)" manufactured by Rigaku Co., Ltd.
Incident X-ray: Cu-Kα ray (λ = 0.15405 nm)
Tube voltage: 40kV
Tube current: 20mA
Sampling width: 0.004°
Scan speed: 0.2°/min 2θ scan range: 40° to 80°

Using the acquired X-ray diffraction profile, a Williamson-Hall plot is created by the method described above. Then, after calculating the non-uniform strain h from the slope of the approximate straight line in the Williamson-Hall plot, the value of the dislocation density ρ can be calculated by substituting the obtained value of h into the above equation (2). Table 2 shows the dislocation density ρ of the test material. The "L×ρ" column in Table 2 shows the value of the product of the value of the total length L of the perimeter of the second phase grains calculated by the method described above and the value of the dislocation density ρ.

・Conductivity E
For the measurement of the conductivity E, for example, a conductivity meter (“Sigmatest 2.069” manufactured by Nippon Förster Co., Ltd.) can be used. Table 2 shows the conductivity E of the test material at 25°C. In order to set the temperature of the test material to 25.degree. Moreover, when using the said conductivity meter, a measurement frequency can be 480 kHz, for example.

[Crystal grain morphology]
The test material is cut parallel to the rolling direction to expose the L-ST plane. After the L-ST surface is polished, anodization is performed to form an oxide film having a polarizing property that depends on the crystal orientation on the surface of the sample. Thereafter, using a polarizing microscope, three randomly selected observation positions from the L-ST plane are observed at a magnification of 100 to obtain microscope images. Also, using an image processing device or the like, the aspect ratio, that is, the ratio of the length of the crystal grain to the thickness of the crystal grain is calculated for each crystal grain in the microscopic image.

When no equiaxed crystal grains (that is, recrystallized grains) are present in the microscopic image and the average aspect ratio is 10 or more, the test material is composed of a fibrous structure. If there are equiaxed crystal grains in the microscopic image, or if the average aspect ratio is less than 10, it is determined that the test material contains an equiaxed structure. . If the aspect ratio of the crystal grains is extremely high, the number of crystal grains whose both ends in the rolling direction are within the field of view decreases, and the average aspect ratio cannot be calculated accurately. In this case, by comparing with a sample having an average aspect ratio of 10, it is determined whether or not the average aspect ratio is 10 or more.

[Correction loss factor η _c ]
First, a strip test piece with a length of 60 mm and a width of 8 mm taken from a test material is used to measure the loss factor η by the free resonance method.

A free resonance type internal friction measuring device (“JE-RT” manufactured by Technoplus Japan Co., Ltd.) can be used to measure the loss factor η. As shown in FIG. 3 , the measuring device 2 has a drive electrode 21 and an amplitude sensor 22 facing the drive electrode 21 . A strip test piece S is horizontally arranged between the driving electrode 21 and the amplitude sensor 22, and fixed with a fine wire 23 at a position that becomes a vibration node. By applying an alternating current to the drive electrode 21 in this state to apply a Coulomb force to the strip test piece S, the strip test piece S can be vibrated. By measuring the amplitude of the strip test piece S using the amplitude sensor 22, the vibration waveform can be obtained.

In this example, an electrostatic force is generated from the drive electrode 21 to forcibly vibrate the strip test piece S, and the amplitude is measured. At this time, by vibrating the strip test piece S while sweeping the vibration frequency, an amplitude-frequency curve as shown in FIG. 4 can be obtained. The vertical axis in FIG. 4 is the common logarithm of amplitude, and the horizontal axis is frequency (Hz).

The loss factor η of the test material can be calculated by the half width method based on the amplitude-frequency curve shown in FIG. First, the frequency at which the amplitude becomes maximum on the amplitude-frequency curve is obtained, and this frequency is defined as the resonance frequency f ₀ . Next, the half width Δf of the resonance peak is obtained. The half width Δf can be specifically calculated as follows. First, in the frequency range lower than the resonance frequency f ₀ , the frequency f ₁ at which the amplitude value is half the amplitude value A ₀ at the resonance frequency f ₀ is obtained. Next, a frequency f ₂ is obtained at which the amplitude value is 1/2 of the amplitude value A ₀ at the resonance frequency f ₀ in the frequency range higher than the resonance frequency f ₀ . The value of the difference f ₂ -f ₁ between the frequency f ₂ and the frequency f ₁ obtained in this manner is the half width Δf.

The loss factor η can be calculated by substituting the resonance frequency f ₀ and the half width Δf obtained above into the following equation (5).

By substituting the loss factor η thus obtained into the following equation (4), the corrected loss factor η _c can be calculated. Table 2 shows the corrected loss factor η _c of the test material.
_ηc = η - 0.556 x t ^-2.434 + 1.5 (4)

As shown in Tables 1 and 2, the values of the metallographic factor F in test materials 1 to 11 and test material 13 are within the specified range. Therefore, the value of the corrected loss factor η _c of these test materials is 1.6×10 ⁻³ or more. Therefore, these test materials have excellent damping properties.

The value of metallographic factor F in test material 12 and test material 14 is smaller than the specified range. Therefore, the damping properties of these test materials are inferior to those of the test materials 1 to 11 and the test material 13.

1 aluminum alloy material 11 Al matrix 12 second phase particles

Claims (4)

An aluminum alloy material having an Al matrix and second phase particles dispersed in the Al matrix,
The aluminum alloy material has a chemical composition containing 0.30 to 3.0% by mass of Fe, with the balance being Al and unavoidable impurities,
An aluminum alloy material having a value of a metallographic factor F represented by the following formula (1) of 0.005 or more.
F=A・ρ・L・exp(B・E) (1)
(However, L in the above formula (1) is the total circumference length [μm/μm ² ] of the second phase particles having an equivalent circle diameter of 0.2 μm or more among the second phase particles existing in an arbitrary cross section, ρ is the dislocation density [μm ⁻² ], E is the electrical conductivity [%IACS] at 25° C., A and B are correction coefficients determined according to the chemical composition of the aluminum alloy material, and 0.2× 10 ⁻¹⁵ ≦A≦20×10 ⁻¹⁵ and 0.1≦B≦1.0.) 2. The aluminum alloy material according to claim 1 , further comprising Mn: 0.10 to 1.50% by mass. The aluminum alloy material further includes Si: 0.0050 to 3.0 mass%, Cu: 0.0030 to 0.10 mass%, Mg: 0.0050 to 3.0 mass%, Zn: 0.10 to 0.50% by mass, Ni: 0.050 to 0.30% by mass, Cr: 0.050 to 0.30% by mass, Ti: 0.050 to 0.30% by mass, V: 0.050 to 0.05% by mass 3. The aluminum alloy material according to claim 1 , containing one or more of 30% by mass and Zr: 0.0010 to 0.30% by mass. The aluminum alloy material according to any one of claims 1 to 3, wherein said aluminum alloy material has a fibrous structure.

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