JP6997984B2 - A powder for three-dimensional laminated modeling containing heterogeneous nuclear particles, a model using the powder, and a method for manufacturing the model. - Google Patents

Description

In the three-dimensional laminated molding technique of metal, the present invention relates to a metal powder for three-dimensional laminated molding in which foreign nuclear particles are mixed with a base metal powder, and a shaped body thereof.

In recent years, a new processing method called Adaptive Manufacturing (AM) has attracted attention. This is a method of modeling a three-dimensional structure based on digital data by Computer-aided design (CAD).
It is called a three-dimensional layered molding method or a 3D printer technology.

In Japan, the resin-based three-dimensional laminated molding method was quickly put into practical use, and exhibits and prototypes were created (
It is used for Rapid prototyping) and the like. The resin-based three-dimensional laminated molding method uses a photocurable resin or a thermosetting resin, that is, a chemical reaction for molding, so that it has the advantage of high molding speed, but has the disadvantage of being inferior in strength and durability. Have. Therefore, when manufacturing a higher-end product that requires high strength and high durability, a three-dimensional laminated metal molding technique is required. However, the fact is that the three-dimensional laminated molding technology for metals is far behind that of resin-based ones.

The three-dimensional laminated metal molding technology is roughly divided into a powder bed melting method and a directed energy deposition method. In the powder bed melting method, the metal powder spread uniformly on the stage is irradiated with a laser or an electron beam along the slice data of the three-dimensional data obtained by CAD to locally and selectively melt and solidify the metal powder. This is a method of producing a three-dimensional structure by repeating the process. On the other hand, the directed energy deposition method uses a laser or an electron beam as a heat source as described above, but is a method of directly supplying the metal powder to the irradiation position. That is, it is a three-dimensional laminated molding method similar to laser cladding (overlay welding).

As described above, in the three-dimensional laminated metal molding method, it is necessary to use the melting and solidification peculiar to the metal as an elementary process, so that internal vacancies due to undissolved powder and volume shrinkage during cooling are likely to be formed. In addition, there is a potential problem that a coarse non-uniform structure (columnar structure) similar to a cast structure is formed, the strength is lowered, and at the same time, anisotropy is generated in the mechanical properties. In addition, a technique for selectively melting a metal having a high melting point and a technique for preventing metal oxidation at that time must be incorporated into the device, which has a drawback that the device itself is expensive. For the above reasons, the three-dimensional laminated molding method of metal is delayed in development compared to that of resin, and has the disadvantage that it is inferior in mechanical properties to metal products manufactured by conventional processing methods and manufacturing methods. Therefore, the scope of application of the product is limited. Since the demand for three-dimensional laminated metal molding technology is expected to increase further in the future, it is desired to develop high-quality laminated molded products that can be used in various situations and usage environments.

Regarding the current solution to the above problem, there is further improvement of a device capable of irradiating a high-power laser or an electron beam, or optimization of modeling conditions and the like. While these solutions have some effect, they come with financial or time costs.

On the other hand, although the conventional metal powder used in the three-dimensional laminated metal molding technology has been conditioned, it has not been substantially improved. In other processing technologies that have been industrially applied in the past, materials suitable for the processing technology have been developed, and the quality and its characteristics have been improved. With regard to 3D laminated modeling technology, quality and specific improvements are expected by developing materials that specialize in this method. To summarize the above, it is desired to develop a metal powder for three-dimensional laminated modeling.

Toshihiko Ozeki: Solidification and solidification structure control of weld metal, Journal of Japan Welding Society, 70 (2001) Yoshimi Watanabe, Takashi Sato: Grain refinement of cast aluminum materials with heterogeneous nuclei with small inconsistencies, Light Metals, 64 (2014) Masaharu Kato: Materia, 56 (2017) Teruo Kishi: Titanium Technical Guide, Otsuru Uchida, (1993) A. Simchi, H.M. Pohl: Mater. Sci. Eng. , A 359 (2003) J. M. Gregg, H. et al. K. D. H. Badeshia: Acta Mater. 45 (1997)

The problem of the present invention solves the above-mentioned conventional problems. Three-dimensional that enhances energy efficiency while ensuring the quality of the model by suppressing the formation of defects such as internal pores and the formation of coarse internal structures, which is a problem in the three-dimensional laminated metal molding method. Raw material powder for laminated modeling,
It is to provide a model body using it and the manufacturing method of the model body.

(1) Melt the necessary part of the metal powder used as a raw material to form a three-dimensional structure.
The metal powder used in the three-dimensional laminated molding method that solidifies and repeats this, has a melting point higher than the melting point of the base metal powder and the base metal powder, and has an atomic arrangement with respect to the base metal powder. It is a metal powder for three-dimensional laminated molding characterized by containing at least one kind of heteronuclear particles having high consistency. That is, the metal powder is a mixed powder.
"Melting and solidifying the required part of the metal powder for three-dimensional laminated molding" means that the powder is evenly spread (powder bed) in the powder bed melting method and supplied from the supply nozzle in the directional energy deposition method. A high-energy beam such as a laser or an electron beam is scanned along the two-dimensional slice data of the CAD data prepared in advance with respect to the powder to be melted and solidified. In the three-dimensional laminated modeling method, this is repeated to form a three-dimensional structure.

（式中の（ｈｋｌ）ｓは異質核粒子の低次指数面、［ｕｖｗ］ｓは（ｈｋｌ）ｓ面の低
次指数方向、（ｈｋｌ）ｎは核生成する金属の低次指数面、［ｕｖｗ］ｎは（ｈｋｌ）ｎ
面の低次指数方向、ｄ［ｕｖｗ］ｓは［ｕｖｗ］ｓ方向に沿った原子間距離、ｄ［ｕｖｗ
］ｎは［ｕｖｗ］ｎ方向に沿った原子間距離、θは［ｕｖｗ］ｓと［ｕｖｗ］ｎとの間の
角度を表している。）

（式中、ε_ｘおよびε_ｙはそれぞれ異質核相の格子と凝固相の格子の各々で直交する主軸
ｘおよびｙに沿った主軸ひずみであり、ε_ｘおよびε_ｙは以下の式（３）および（４）で
算出される。）

（式中、ｘⁱ、ｙⁱおよびｘ^ｊ、ｙ^ｊはそれぞれ物質ｉおよび物質ｊの主軸ひずみ方向であ
り、ａ_ｉおよびａ_ｊはそれぞれ物質ｉおよび物質ｊの格子定数である。） (2) The heteronuclear particles are characterized in that the plane mismatch degree represented by the formula (1) is 10% or less, or the parameter M represented by the formula (2) is 25 × 10 ^-3 or less. The metal powder for three-dimensional laminated modeling according to (1).

(In the equation, (hkl) s is the low-order exponential plane of the foreign nuclear particle, [uvw] s is the low-order exponential plane of the (hkl) s plane, and (hkl) n is the low-order exponential plane of the nucleating metal. uvw] n is (hkl) n
Low-order exponential direction of the surface, d [uvw] s is the interatomic distance along the [uvw] s direction, d [uvw]
] N represents the interatomic distance along the [uvw] n direction, and θ represents the angle between [uvw] s and [uvw] n. )

(In the equation, ε _x and ε _y are the main axis strains along the main axes x and y that are orthogonal to each other in the lattice of the heterogeneous nuclear phase and the lattice of the solidification phase, respectively, and ε _x and ε _y are the following equations (3). And calculated in (4).)

(In the equation, x ⁱ , y ⁱ and x ^j , y ^j are the main axis strain directions of the substance i and the substance j, respectively, and a _i and a _j are the lattice constants of the substance i and the substance j, respectively.)

(3) The volume ratio of the heterogeneous nuclear particles to the base metal powder is 1.0% or less, (1).
Or the metal powder for three-dimensional laminated modeling according to (2). Here, since there is at least one type of heterogeneous nuclear particles, for example, if there is only one type of heterogeneous nuclear particles, the volume ratio of the one type of heterogeneous nuclear particles to the base metal powder is 1.0% or less. Become. If there are two types of heterogeneous nuclear particles, the total volume fraction of the heterogeneous nuclear particles with respect to the base metal powder is 1.0% or less. That is, "the volume ratio of the heterogeneous nuclear particles to the base metal powder is 1.0% or less" means
It means "the total volume fraction of the heterogeneous nuclear particles with respect to the base metal powder is 1.0% or less".
It is desirable that the heterogeneous nuclear particles have a finer or similar particle size to the base metal powder. Further, the heterogeneous nuclear particles are mixed so as to be uniformly distributed in the base metal powder.
(4) The base metal powder is one kind of metal powder selected from Ti alloy powder, maraging steel powder, nickel alloy powder, pure aluminum and aluminum alloy powder (1).
)-(3). The metal powder for three-dimensional laminated modeling according to any one of (3).

(5) The heteronuclear particle is at least one kind selected from TiC, TiN and TiB, which is any one of (1) to (4) that acts as a nucleus of crystal growth during solidification. It is the metal powder for three-dimensional laminated modeling according to one.
(6) Using the metal powder for three-dimensional laminated molding according to any one of (1) to (5) as a raw material, only the base metal powder of the metal powder for three-dimensional laminated molding is melted and solidified. It is a laminated molding method that acts as a nucleus for crystal growth of the base metal in which the heterogeneous nuclear particles are melted by molding according to conditions.

(7) It is a modeled body manufactured by the laminated modeling method described in (6).

Laminated modeling using the powder bed melting method is performed, and the internal pores, internal structure, or Vickers hardness of the produced structure is evaluated, and the usefulness of the metal powder is confirmed.

By using the powder for laminated molding according to the present invention, it is possible to obtain a shaped body which is a three-dimensional laminated molding of a metal in which the formation of defects such as internal pores is suppressed and the formation of a coarse internal structure is suppressed.

It is a graph which plotted the parameter M with respect to the plane inconsistency in this invention. It is a figure which shows the procedure of manufacturing the shaped body which is characterized by high strength and high formability in the three-dimensional laminated molding method for metal by this invention. For Example 1, a scanning type of a laminated molding powder produced by mixing 0.3 vol% of TiC particles having a particle size of 2-5 μm with a Ti-6Al-4V alloy powder having a particle size of 45 μm or less. It is an electron micrograph. The figure which shows the outline of the drawing condition of the laser at the time of performing modeling about Example 1. FIG. The arrows in the figure indicate the direction of laser scanning. FIG. 1 is an optical micrograph of the inside of an additive-free material and an S3-TiC additive modeled using energy densities of 108 J / mm ³ , 182 J / mm ³ and 404 J / mm ³ for Example 1. About Example 1, it is a graph which plotted the relative density (%) measured by the Archimedes method in the additive-free material and the TiC additive with respect to the energy density converted from the modeling condition. About Example 1, it is an internal structure observed on the laminated surface of (a) additive-free material and (b) S3-TiC additive which was formed using the energy density of 540 J / mm ³ . About Example 1, it is a graph which plotted (a) the size quantification result of the old β particle diameter and (b) the Vickers hardness measurement result on the laminated surface of the modeled body with respect to the energy density converted from the modeling conditions. It is a figure which shows the outline of the drawing condition of the laser at the time of performing modeling about Example 2. The arrows in the figure indicate the direction of laser scanning. For Example 2, the internal structure observed in the vertical cross section of (a) additive-free material, (b) S10-TiC additive, and (d) M10-TiC additive formed using an energy density of 625 J / mm ³ . Low-magnification photographs, (c) and (e), are high-magnification photographs of the internal structure observed in the vertical cross section of the S10-TiC additive and the M10-TiC additive, respectively. About Example 2, it is an internal structure observed in the vertical cross section of (a) additive-free material and (b) S10-TiC additive which was formed using the energy density of 625 J / mm ³ . It is a graph which plotted the Vickers hardness measurement result with respect to the energy density converted from the modeling condition.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be made without departing from the scope of the invention.

In the present invention, with respect to a novel metal powder for three-dimensional laminated molding based on the heterogeneous nucleation theory, the melting point is higher than that of the base metal, and the atomic arrangement is consistent with the phase that becomes the primary crystal of the base metal. A metal powder for three-dimensional laminated molding is prepared by premixing a good heterogeneous nucleus. When the produced powder material is irradiated with a high-energy beam such as a laser or an electron beam that melts only the base metal powder, only the base metal powder melts and foreign nuclei particles are solidified during the subsequent cooling process. Will act as the core of crystal growth. In addition, when the wettability to the molten base metal is good, by optimizing the size and distribution of the heteronuclear particles, the expansion of the molten region is achieved under the same molding conditions, and uniform solidification in various places is achieved. By promoting the above, it becomes possible to suppress the formation of a high-density model with few internal pores and the development of coarse and non-uniform internal tissue. In addition, it is possible that the heterogeneous nuclear particles impede grain growth (pinning effect) due to repeated heat input, and it is expected that a fine structure will be maintained even after modeling.

Structure control based on the heterogeneous nucleation theory is also used in welding engineering and casting engineering (Non-Patent Document 1). However, the disclosed invention is different from the methods used in welding engineering and casting engineering. In welding engineering, the main target metal is steel material, and a large amount of oxide is added to the weld by using a wire containing oxide flux or oxide, or by using oxygen gas as the shield gas. Fine texture is obtained by forming and making this a nuclear production site. On the other hand, in casting engineering, microstructure miniaturization is achieved by adding foreign nuclear particles to molten metal. Therefore, in both cases, it is necessary to insert a secondary step in the process.

式中の（ｈｋｌ）ｓは異質核粒子の低次指数面、［ｕｖｗ］ｓは（ｈｋｌ）ｓ面の低次
指数方向、（ｈｋｌ）ｎは核生成する金属の低次指数面、［ｕｖｗ］ｎは（ｈｋｌ）ｎ面
の低次指数方向、ｄ［ｕｖｗ］ｓは［ｕｖｗ］ｓ方向に沿った原子間距離、ｄ［ｕｖｗ］
ｎは［ｕｖｗ］ｎ方向に沿った原子間距離、θは［ｕｖｗ］ｓと［ｕｖｗ］ｎとの間の角
度を表している。 Inconsistency is an index for selecting and evaluating foreign nuclear materials that exert the above-mentioned effects. If the degree of inconsistency is 10% or less, it is considered to act as an effective foreign nucleus. In addition, since the case where the crystal structure of the solidified metal and the heterogeneous nuclear particles are different is taken into consideration, the plane inconsistency calculated by the equation (1) is the evaluation index, and similarly, if it is 10% or less, it is an effective heterogeneity. It is considered to be the nucleus. in this case,
The directional relationship between the solidified metal and the heteronuclear particles is only for the low exponential plane / orientation.

In the formula, (hkl) s is the low-order exponential plane of the heterogeneous nuclear particle, [uvw] s is the low-order exponential plane of the (hkl) s plane, and (hkl) n is the low-order exponential plane of the nucleated metal, [uvw. ] N is the low-order exponential direction of the (hkl) n-plane, d [uvw] s is the interatomic distance along the [uvw] s direction, d [uvw]
n represents the interatomic distance along the [uvw] n direction, and θ represents the angle between [uvw] s and [uvw] n.

式中、ε_ｘおよびε_ｙはそれぞれ異質核相の格子と凝固相の格子の各々で直交する主軸ｘ
およびｙに沿った主軸ひずみである。 Recently, not only the above-mentioned plane mismatch, but also the parameter M (which is approximately proportional to the elastic strain).
The formula (2) (Non-Patent Document 3)) has been adopted as a new index for evaluating the performance of heterogeneous nuclear particles. The parameter M is calculated by the following equation, and the smaller this value is, the smaller the energy required for nucleation is, so it is considered to act as an effective heterogeneous nucleus.

In the equation, ε _x and ε _y are the main axes x orthogonal to each other in the lattice of the heterogeneous nuclear phase and the lattice of the solidified phase, respectively.
And the spindle strain along y.

式中、ｘⁱ、ｙⁱおよびｘ^ｊ、ｙ^ｊはそれぞれ物質ｉおよび物質ｊの主軸ひずみ方向であり
、ａ_ｉおよびａ_ｊはそれぞれ物質ｉおよび物質ｊの格子定数である。 Further, ε _x and ε _y are calculated by the following equations (3) and (4).

In the equation, x ⁱ , y ⁱ and x ^j , y ^j are the main axis strain directions of the substance i and the substance j, respectively, and a _i and a _j are the lattice constants of the substance i and the substance j, respectively.

The parameter M can be considered not only for the low exponential plane / orientation but also for all crystal orientation relations. Further, the parameter M is a parameter having a physical meaning because it is approximately proportional to the elastic strain energy due to the misfit strain introduced at the heterophase interface.

In the present invention, the above-mentioned planar inconsistency, the consistency evaluation parameter of the atomic arrangement represented by the parameter M, and the heterogeneity that becomes the heterogeneous solidified nucleus effective for the base metal when used for the two parameters of the melting point. Provided is a metal powder for laminated molding produced by selecting nuclear particles and mixing them with a base metal powder. At this time, the base metal has a high melting point and the parameter M is 2.
A compound of 5 × 10 ^-3 is used as a heteronuclear substance. Here, the upper limit of the parameter M is assumed to be 10% or less, which is a condition for working as an effective heteronuclear when converted into a plane inconsistency, and the metal listed as a candidate for heteronuclear particles in Example 1 described later. It was determined from the results of evaluation of the intermetallic compound, TiC, TiN and TiB parameter M. A graph in which the parameter M is plotted against the plane inconsistency is shown in FIG.

The evaluation by the parameter M will be described with an example. For example, body-centered cubic structure (b)
Face-centered cubic structure (face-centered cubic structure) as a heterogeneous nucleus with respect to the primary crystal β phase of the Ti-6Al-4V alloy having cc).
When considering TiC particles having an fcc) -based crystal structure, assuming that the β phase of the Ti-6Al-4V alloy is the same as the lattice constant of the β phase of pure Ti, each lattice constant is the β phase. Is 0.328 nm and TiC is 0.4327 nm. The interface between the β phase and TiC during solidification is parallel to each (100) plane, and the β phase [011] direction and TiC [001]
Considering that the crystal orientation relationship in which the directions are parallel is established, ε _x and ε _y are both 0.0672 from the equations (2), (3) and (4), so that the value of the parameter M is 12 It becomes .03 × 10 ^-3 . Therefore, in this case, TiC can be an effective heteronuclear for the primary β phase of the Ti-6Al-4V alloy.

There are innumerable crystal orientation relationships at the interface between the base metal and the heterogeneous nucleus, but in this disclosure, considering the low exponential plane, the one with the smallest value is the parameter M of the substance with respect to the base metal. And.

By using such a metal powder for laminated molding, it is possible to manufacture a high-quality modeled body having a fine structure with few defects such as internal pores, and thus modeling even with a heat source having lower energy. It is an important feature of the present invention that it enables energy saving in the laminated molding process.

The present invention is an invention common to the metal laminated molding method. Therefore, it is also a feature of the present invention that it can be applied to all metal laminated molding techniques. It is also important of the present invention that the technique is applicable to all metals or alloy types as long as there is a heterogeneous nucleus that has a melting point higher than that of the base metal and satisfies the above parameter M. It is a feature.

As described in paragraph [0029], the present invention is expected to exert a wide range of effects on the metal laminated molding method, but the present invention discloses a powder bed melting method using a laser as an example. The case of the metal powder for laminated molding is shown.

Based on FIG. 2, the laminated modeling method by the powder bed melting method according to the present disclosure will be described. First, the powder supply tank 1 is filled with the metal powder 2. The base plate 3 is lowered by the stacking pitch, and conversely, the powder supply tank is raised by the stacking pitch (FIG. 2A). The mixed powder is spread on the base plate 3 by a roller called a recoater 4 to form a uniform powder surface (FIG. 2 (b)). From the laser source 5 on the upper part of the base plate 3, laser irradiation 7 is performed according to the modeling program prepared in advance to perform modeling for one layer (FIG. 2 (c)). The model 8 is obtained by repeating the modeling (FIG. 2 (d)).

When searching for a heterogeneous solidified nucleus for the base metal, the parameter M shown in (Equation 2) is used for the consistency of the atomic arrangement. It is produced by uniformly mixing a mixed powder containing heterogeneous solidified nuclei particles having a high melting point and high atomic arrangement consistency with respect to the base metal powder by a powder mixing device. The mixed powder produced as described above is used as a metal powder for laminated modeling.

The modeled body formed by using the metal powder for laminated modeling and the modeled body formed only by the base metal powder produced for comparison were evaluated, and the metal for laminated modeling invented by the present disclosure to which the heterogeneous solidified nucleus was added was evaluated. The usefulness of the powder is shown.

The main metals used for laminated metal molding include Ti-6Al-4V, nickel alloys, maraging steels, pure aluminum, aluminum alloys and the like. Considering the case where the primary crystal is a body-centered cubic (bcc) or a face-centered cubic (fcc) from these metals, in Example 1, Ti-6Al-4V in which the primary crystal is a bcc phase is used. Select, and in Example 2, the primary crystal is f.
Pure aluminum, which is the cc phase, was selected as the base metal. As mentioned in paragraph [0029], the present invention is not limited to the material system.

(Example 1)
The Ti-6Al-4V alloy is classified as an α + β type titanium alloy and is an important alloy used for engine members in the aerospace field. The crystal structure of the α phase is the closest hexagonal crystal (hcp), and the β phase is the body-centered cubic crystal (bcc). In Ti-6Al-4V, the β phase first crystallizes as a primary crystal. After that, a phase transformation occurs at the transformation point of 995 ° C., the β phase is transformed into the α phase, and finally the two phases of the α phase and the β phase coexist at room temperature (Non-Patent Document 4). .. Therefore, Ti-6Al-
When 4V is selected as the matrix metal, a foreign substance having a high atomic arrangement consistency with respect to the primary β phase of Ti-6Al-4V and a high melting point with respect to the same alloy becomes a heterogeneous nuclear substance.

Therefore, the parameter M for the primary β phase of Ti-6Al-4V is obtained. Table 1 shows Ti
Various intermetallic compounds and Ti carbides, nitrides and borides whose constituent elements are T.
The melting points, crystal structures, lattice constants and parameters M calculated using the equations (2), (3) and (4) of iC, TiN and TiB are shown. The values calculated using the equation (1) are also shown for the plane inconsistency used in the past. Here, the parameters M and the plane mismatch degree shown in Table 1 are calculated assuming the orientation relationship on the low exponential plane in the primary β phase / heterocoagulated nucleus of Ti-6Al-4V. As shown in Table 1, since the plane inconsistency is 10% or less in any heterogeneous nuclear material, it is considered that it works effectively as a heterogeneous nucleus. Among them, TiC particles were selected in the present invention as having a melting point higher than Ti-6Al-4V and a small parameter M.

It is not desirable to impair the composition of the alloy in the metal, but in the model of the present invention, the addition of foreign nuclei particles to the base metal is very small, so the change in composition is very small. .. On the contrary, the added heterogeneous nuclei are not only expected to pin the crystal grain growth due to the unavoidable heating added at the time of the subsequent laminated molding even after solidification, and to prevent the coarsening of the crystal grains. , It can also be expected to play a role as a strengthening phase that hinders the movement of dislocations.

Ti-6Al-4V is selected as the base metal powder and TiC is selected as the heterogeneous nuclear particles, and these are mixed to prepare a three-dimensional laminated modeling powder. For Ti-6Al-4V powder and TiC particles, the particle size distribution is made uniform by sieving, the particle size of Ti-6Al-4V powder is selected to be 45 μm or less, and the particle size of TiC is 2-5 μm or 45 μm or less. Selected. Here, due to the nature of the sieve, the powder having a particle size of 2-5 μm is mixed in the powder having a particle size of 45 μm or less.
The amount is small. Therefore, the effects of the two particle diameters, which are equivalent to the Ti-6Al-4V particle diameter of the base metal powder or the particle diameter of 1/10, were investigated. Also, Ti-6Al
-4V is a gas atomizing powder which is a spherical particle, and TiC particle is a crushed powder which is a polygonal particle. The gas atomizing powder is a powder produced by the gas atomizing method, and is produced by a method of pulverizing by blowing a high-pressure gas when the molten metal is allowed to flow down from the upper stage.

The amount of 2-5 μm TiC particles added is 0.1 vol%, 0.3 vol% or 0.5 vo.
Let l%, and the amount of TiC particles added of 45 μm or less is 0.1 vol% or 0.5 vol%.
And said. The TiC particles were placed in a 500 ml container together with Ti-6Al-4V powder, and mixed for 1 hour using a Turbler mixer powder mixing device so as to be uniform. An example of the produced powder for laminated modeling is illustrated in FIG. FIG. 3 is a scanning electron micrograph of a mixed powder prepared by mixing 0.3 vol% of 2-5 μm TiC particles 9 with Ti-6Al-4V powder 10. The mixed powder 11 in which the TiC particles 9 were attached to the surface of the spherical Ti-6Al-4V particles 10 could be observed. In addition, in order to show the effect of adding TiC, Ti-6Al-4V powder 10 not mixed with TiC particles 9 was also prepared and used for modeling. When the volume fraction to be added is the same, if the particle size of the TiC particles 9 is reduced, the number density of the TiC particles 9 existing per unit volume increases.

In Example 1, a sample formed from a powder containing only Ti-6Al-4V alloy powder was used as an additive-free material.
A sample formed by mixing TiC particles 9 and 11 with Ti-6Al-4V alloy powder is Ti.
It is called a C additive. When TiC particles 9 having a particle size of 2-5 μm are used, the amount of each addition,
0.1 vol%, 0.3 vol% and 0.5 vol% are S1, S3 and S5, respectively.
When TiC particles 19 having a particle size of 45 μm or less are used, the added amounts of 0.1 vol% and 0.5 vol% are M1 and M5, respectively. For example, when 0.3 vol% of TiC particles having a particle size of 2-5 μm is added, it is referred to as an S3-TiC additive.

Table 2 summarizes the laminated modeling conditions used in Example 1. In Example 1, the scanning speed, the scanning pitch, and the stacking pitch were fixed, and the output at the time of modeling was changed to perform stacking modeling. Further, FIG. 4 shows the depiction conditions of the laser scanning used in Example 1. In the preheating step, the laser is scanned in a circular region having a diameter of 10.0 mm surrounded by the residual heat outer peripheral portion 12 according to a grid trace. In the modeling step, the laser is similarly irradiated to the rectangular region surrounded by the outer peripheral portion 14 of the modeled body having a length of 5 mm and a width of 7.5 mm, which are the dimensions of the modeled body. Using the above-mentioned conditions, modeling was performed until a modeled body having a height of 5 mm was obtained.

Ｅはエネルギー密度［Ｊ/ｍｍ^３］、Ｐはレーザー出力［Ｗ］、ｖは走査速度［ｍｍ/ｓ］
、ｓは走査ピッチ［ｍｍ］、ｔは積層ピッチ［ｍｍ］である（非特許文献５）。 Further, from the above-mentioned laminated molding conditions, the introduction energy per unit volume by laser irradiation (energy density [J / mm ³ ]) was calculated using the following formula, and the relative density at each energy density, the old β particle size, Evaluate the Vickers hardness.

E is the energy density [J / mm ³ ], P is the laser output [W], and v is the scanning speed [mm / s].
, S is the scanning pitch [mm], and t is the stacking pitch [mm] (Non-Patent Document 5).

FIG. 5 is an optical micrograph of a vertical cross section of an additive-free material and an S3-TiC additive modeled with 108 [J / mm ³ ], 182 [J / mm ³ ] and 404 [J / mm ³ ]. In the molding with low energy density, many internal pores called pores 15 were observed, and the area ratio decreased as the energy density increased. Comparing with and without TiC addition, S3-T
It was found that the porosity of the iC additive material was lower than that of the additive-free material, and the effect of TiC addition could be confirmed.

The relative density of the produced model is evaluated by the Archimedes method, and the energy density calculated by the equation (5) is shown in the graph of FIG. 6 on the horizontal axis. Here, the Archimedes method is a relatively simple relative density measuring method using water and a scale, and measures the relative density by measuring the buoyancy caused by the density difference between water and the object.

As shown in FIG. 6, it was confirmed that the relative densities of all the shaped objects increased as the energy density increased. It was also confirmed that the sample with the highest relative density was the S3-TiC additive. Under the molding conditions on the low energy side of 200 J / mm ³ or less, the T produced this time
It can be seen that by using the metal powder for laminated modeling containing iC particles, it is possible to produce a model having a higher relative density than the additive-free material. Therefore, it is possible to perform modeling with a laser having a lower energy density, and this result contributes to energy saving of the process in the three-dimensional laminated modeling technology. Hereafter, the comparison results of the internal structure observation and the Vickers hardness test for the additive-free material and the S3-TiC additive material are shown.

The internal structure was observed with an optical microscope using the upper surface of the modeled body (the surface parallel to the laminated surface) as the observation surface. An aqueous solution of nitric acid hydrofluoric acid was used for corrosion. The observation results are shown in FIG. Compared with the internal structure of the additive-free material shown in FIG. 7 (a), a large number of primary crystal β grain boundaries 16 were observed in the internal structure of the S3-TiC additive shown in FIG. 7 (b), and the structure became finer. You can check the situation. On the other hand, TiC particles cannot be clearly observed because the α phase structure is fine.

FIG. 8A shows the size quantification result of the old β particle size on the laminated surface. It can be confirmed that the structure size tends to be coarsened as the energy density of the laser in the molding increases, while the internal structure of the S3-TiC additive can be confirmed to be finer.
Therefore, it was shown that a finer structure can be obtained by performing laminated modeling using the metal powder for laminated modeling disclosed in the present invention.

FIG. 8B shows the Vickers hardness test results on the laminated surface. The Vickers hardness test is a kind of mechanical property evaluation method for evaluating the hardness of a material from the pressing depth when a diamond indenter is pressed into the surface of a sample with a predetermined load. The S3-TiC additive exhibits a higher Vickers hardness than the additive-free material. This result shows that it is possible to obtain a higher-strength modeled body by performing layered modeling using the metal powder for layered modeling disclosed in the present invention.

On the other hand, although the effect of adding TiC on the miniaturization of β particle size was confirmed, the miniaturization of α structure was not achieved. This is because the α phase of the Ti-6Al-4V alloy has an hcp structure, so the consistency at the interface with TiC is lower than that of the β phase, and it does not act as a heterogeneous nucleus for the α phase that nucleates next to the β phase. Because.

The present invention discloses a method in which a powder melted by a high-energy beam is added with heterogeneous nuclear particles which are the nuclei of crystal growth when it is subsequently solidified in a layered stereolithography method. On the other hand, the heterogeneous nuclear particles can become the nucleus of crystal growth even in the phase transformation in the solid phase when the consistency with the generated phase is good (Non-Patent Document 6).

In the present disclosure, only TiC is added as the heterogeneous nuclear particles to the β phase, but by compound-adding the heterogeneous nuclear particles having good interface consistency to the α phase, further microstructure and microstructure can be achieved. Vickers hardness is expected to increase.

The S3-TiC additive produced in Example 1 has fewer internal pores and a finer structure than the additive-free material. Therefore, it is expected that the tensile properties (tensile strength and spread) will be improved and the impact properties will be improved as compared with the modeled body formed only by the base metal powder. Tensile and Charpy tests are commonly used to evaluate tensile and impact properties, respectively.

The tensile test is a test method in which a test piece defined by JIS standards is subjected to tension until it breaks, and the yield point, tensile strength, elongation, etc. of the test piece are evaluated. In microstructures with more grain boundaries that can interfere with the movement of dislocations in the metal structure responsible for deformation when tension is applied, the yield point and tensile strength are improved and uniform deformation is promoted. Therefore, it is considered that the TiC additive produced in Example 1 exhibits excellent tensile properties because the elongation is also improved.

The Charpy test is a test method for measuring the energy absorbed when a hammer is swung down to break a test piece having a notch (cut portion) defined by the JIS standard. When a large amount of pores are present in the test piece, the energy absorbed is small and it is easily broken. Therefore, it is considered that the TiC additive produced in Example 1 has a large amount of energy absorbed and has high toughness. ..

(Example 2)
Aluminum, which is a kind of light metal, has excellent properties not found in other metals, such as high corrosion resistance, excellent thermal conductivity, electrical conductivity, and being a non-magnetic material. Therefore, it is applied to general structural members such as Shinkansen and automobiles, cutting-edge equipment members in the space and aviation fields of transport aircraft, measuring instruments, medical equipment, and the like. In Example 2, α (hcp) disclosed in Example 1
Face-centered cubic (face-centered cubic) unlike Ti-6Al-4V alloy, which has a two-phase structure of phase + β (bcc) phase.
fcc) When pure aluminum formed by a single-phase structure is used.

The melting point of pure aluminum is approximately 660 ° C., and the fcc phase crystallizes from the liquid phase to form a structure. Therefore, TiC particles, which are heteronuclear particles having a higher melting point than pure aluminum and having good atomic arrangement consistency with respect to the fcc phase of pure aluminum, are mixed with pure aluminum powder.
A metal powder for three-dimensional laminated modeling was produced. The TiC parameter M and plane inconsistency for pure aluminum are 11 × 10 ^-3 and 6.69%, respectively. Similar to Example 1, TiC particles are effective heteronuclear particles because they are smaller than the values defined in the present invention.

Pure aluminum powder is selected as the base metal and TiC particles are selected as the heterogeneous nuclear particles, and these are mixed to prepare a three-dimensional laminated modeling powder. The average particle size of pure aluminum powder is 20μ
The particle sizes of m and TiC particles were selected to be 2-5 μm and 45 μm or less, which were the same as in Example 1. Similar to Example 1, the particle size of each powder is adjusted by a sieve. Therefore, in Example 2,
The case where the TiC particles have a particle size smaller than that of the base metal powder and the case where the particle size is approximately twice that of the base metal powder will be disclosed.

The amount of TiC added was unified to 1.0 vol%, and the mixture was placed in a 500 ml container together with pure aluminum powder and mixed for 1 hour using a Turbler mixer powder mixing device. Hereinafter, in Example 2, a sample formed of a powder containing only aluminum is referred to as an additive-free material, and a sample formed of a powder to which 1.0 vol% of TiC particles is added is referred to as a TiC additive. Also, the particle size is 2-
A sample formed by adding 5 μm TiC particles is an S10-TiC additive, and T of 45 μm or less.
A sample formed by adding iC particles is used as an M10-TiC additive.

Table 3 summarizes the laminated modeling conditions used in Example 2. Further, FIG. 9 shows the depiction conditions of the laser scanning used in Example 2. FIG. 9A shows the depiction condition of the nth layer, and FIG. 9A shows FIG. 9 (a).
b) is a depiction condition for the n + 1th layer. The dimensions of the modeled body were 5 mm in length and 7.5 mm in width, and modeling was performed until the modeled body had a height of 5 mm.

FIG. 10 shows additive-free material, S10-TiC additive material and M10- made at 625 J / mm ² .
It is an optical micrograph observed in the vertical cross section of a TiC additive. In the additive-free material shown in FIG. 10A, the fcc grain boundaries 19 extend along the stacking direction, and therefore, the coarse columnar structure which was the subject of the present invention was developed. On the other hand, in the TiC additive shown in FIGS. 10 (b) and 10 (d), the fcc particle size became finer, and the TiC particles 20 observed in the structure were confirmed. Further, in the S10-TiC additive shown in FIGS. 10 (c) and 10 (e), it is observed that the fcc particle size is further reduced as compared with the M10-TiC additive. This result shows that, when the amount of heteronuclear particles added is the same, the finer the TiC particles, the higher the number density per unit volume.
The result was that the higher number density promoted microstructure miniaturization. In addition, no difference in fcc particle size was confirmed between the lower surface (near the modeling start surface) and the upper surface (near the modeling end surface) of the modeled sample, and the structure did not change in the stacking direction despite repeated heat input. rice field. Therefore, by adding foreign nuclei particles, a pinning effect of suppressing grain growth during reheating was also exhibited.

FIG. 11 is an optical micrograph observed in a horizontal cross section of the S10-TiC additive and the M10-TiC additive formed at 625 J / mm ² . TiC particles could be observed in FIGS. 11 (a) and 11 (b). Also, in the observation in the horizontal cross section, more fcc grain boundaries 19 were observed in the S10-TiC additive than in the M10-TiC additive, and therefore fc.
c It was possible to confirm that the particle size was becoming finer. Therefore, even with pure aluminum in the fcc phase, the effect of micronizing the structure was exhibited by the addition of foreign nuclei particles.

FIG. 12 shows the results of the Vickers hardness test in the horizontal cross section of the additive-free material, the S10-TiC additive material and the M10-TiC additive material. The S10-TiC additive had the highest Vickers hardness, and the M10-TiC additive and the additive-free material had the lowest Vickers hardness in that order. This result is in agreement with the result of microstructure observation, and the Vickers hardness increases as the fcc particle size becomes finer.

From the experimental results disclosed in Examples 1 and 2 described above, it was found that the method of the present invention is applicable to various metals and alloys, and the validity of this method was shown.

Melting and solidifying the necessary parts of the metal powder used as a raw material to form a three-dimensional structure.
It can be used as a laminated modeling method in which this is repeated, that is, as a metal powder for 3D laminated modeling.

1 Powder supply tank 2 Metal powder 3 Base plate 4 Recoater 5 Laser source 7 Laser irradiation
8 Modeled body (three-dimensional structure)
9 TiC particles with a particle size of 2-5 μm (heterogeneous nuclei particles)
10 Ti-6Al-4 powder (base metal powder)
11 Mixed powder (metal powder for 3D laminated modeling)
12 Remaining heat outer circumference 13, 17 Laser scanning direction 14, 18 Model outer circumference 15 Pore 16 β grain boundary 19 fcc grain boundary 20 TiC particles observed in the tissue

Claims (5)

A method for producing the metal powder used in a three-dimensional laminated modeling method in which a portion required for a metal powder used as a raw material for modeling a three-dimensional structure is melted and solidified, and this is repeated.
The metal powder has a melting point higher than the melting point of the base metal powder and the base metal powder, and contains at least one kind of heteronuclear particles having a high atomic arrangement consistency with the base metal powder. ,
The heteronuclear particles are selected so that the plane mismatch degree represented by the formula (1) is 10% or less, or the parameter M represented by the formula (2) is 25 × 10 ^-3 or less. , A method for producing a metal powder for three-dimensional laminated modeling.

(In the equation, (hkl) s is the low-order exponential plane of the foreign nuclear particle, [uvw] s is the low-order exponential plane of the (hkl) s plane, and (hkl) n is the low-order exponential plane of the nucleating metal. uvw] n is the low-order exponential direction of the (hkl) n plane, d [uvw] s is the interatomic distance along the [uvw] s direction, and d [uvw] n is the interatomic distance along the [uvw] n direction. , Θ represent the angle between [uvw] s and [uvw] n.)

(In the equation, εx and εy are the main axis strains along the main axes x and y that are orthogonal to each other in the lattice of the heterogeneous nuclear phase and the lattice of the solidified phase, respectively, and εx and εy are the following equations (3) and (4). It is calculated by.)

(In the equation, xi, yi and xj, yj are the main axis strain directions of the substance i and the substance j, respectively, and ai and aj are the lattice constants of the substance i and the substance j, respectively.) The method for producing a metal powder for three-dimensional laminated molding according to claim 1 , wherein the volume ratio of the heterogeneous nuclear particles to the base metal powder is 1.0% or less. The three-dimensional laminated molding according to claim 1 or 2 , wherein the base metal powder is one kind of metal powder selected from Ti alloy powder, maraging steel powder, nickel alloy powder, pure aluminum and aluminum alloy powder. Method for manufacturing metal powder. 13 . A method for producing metal powder for three-dimensional laminated modeling. Using the metal powder for three-dimensional laminated molding according to any one of claims 1 to 4 as a raw material, molding is performed under molding conditions in which only the base metal powder of the metal powder for three-dimensional laminated molding is melted and solidified. A method for manufacturing a three-dimensional laminated molding using a laminated molding method that acts as a nucleus for crystal growth of the base metal in which the heterogeneous nuclear particles are melted.

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