Copper alloy powder and method for manufacturing laminate shaped article using said copper alloy powder

Abstract

[Problem] To provide a copper alloy powder which is for laminate shaping and from which a laminate shaped article having excellent conductivity and high relative density can be obtained. [Solution] This copper alloy powder for laminate shaping contains Cr, with the remainder consisting of Cu and inevitable impurities, and has a ratio R of 0.1-10, wherein the ratio R is represented by the expression R=Af / Ab (in the expression, Af represents an X-ray absorption spectrum derived from Cr having a face-centered cubic structure, in a spectrum obtained by X-ray absorption near edge structure (XANES) analysis of the copper alloy powder, and Ab represents an X-ray absorption spectrum derived from Cr having a body-centered cubic structure, obtained by XANES analysis of the copper alloy powder).

Description

Copper alloy powder and method for manufacturing layered object using the copper alloy powder

[0001] The present invention relates to a copper alloy powder, and more particularly to a copper alloy powder that can be suitably used for additive manufacturing such as three-dimensional additive manufacturing, and a method for producing an additive manufactured product using the copper alloy powder.

[0002] Three-dimensional additive manufacturing (3D) devices, or so-called 3D printers, capable of rapidly creating components with complex three-dimensional shapes are becoming increasingly popular. Among the methods for producing additively manufactured objects using such 3D printers, powder bed fusion (PBF) is a well-known method for producing metal objects. PBF involves irradiating the surface of a powder bed with energy rays, such as a high-energy laser or electron beam, to sinter or melt and solidify the powder particles. These layers, each several tens of microns thick, are then stacked and repeatedly bonded to produce three-dimensional additively manufactured objects. The L-PBF method, which uses a metal-based powder and a laser as a heat source, is also becoming more practical. L-PBF, which uses metal-based powders such as Co—Cr alloys, titanium alloys, maraging steels, stainless steels, and nickel-based superalloys, produces additively manufactured objects with high processing precision and a high level of finish. Additively manufactured objects suitable for heat-resistant and high-heat applications are also beginning to be commercialized.

[0003] However, the current L-PBF method is limited in the metal base powders that can be used, and the metal products that can be obtained are also limited to a certain range. For example, although copper is a metal with high thermal and electrical conductivity and excellent workability, it is considered difficult to apply the L-PBF method. The main reasons for this are that the energy absorption rate of laser light is extremely low, making it impossible to reach the melting point, and even if it does reach the melting point, its high thermal conductivity causes rapid heat diffusion and prevents sufficient melting. To address this problem, Patent Document 1 reports that using copper alloy powder containing chromium (Cr) reduces thermal conductivity, facilitating additive manufacturing, and that heat treatment of the resulting additive manufactured product exhibits excellent electrical conductivity, thermal conductivity, and mechanical strength.

[0004] Japanese Patent Application Laid-Open No. 2019-070169

[0005] The above-mentioned Patent Document 1 describes that by subjecting an additive manufacturing product obtained using a copper alloy powder containing Cr to a heat treatment at a predetermined temperature for a predetermined time, a Cr phase contained in a supersaturated state in the Cu matrix is ​​precipitated, thereby improving the mechanical strength, electrical conductivity, and thermal conductivity. However, the mechanical strength, electrical conductivity, etc. of the obtained additive manufacturing product itself are not superior, and additive manufacturing products using a copper alloy powder containing Cr are currently inferior to the electrical conductivity and relative density of copper itself.

[0006] Therefore, an object of the present invention is to provide a copper alloy powder for additive manufacturing that can produce additively manufactured articles that have excellent electrical conductivity and a high relative density.

[0007] The inventors of the present invention have discovered that, in a Cr-containing copper alloy powder, by controlling the proportion of Cr dissolved in copper or a Cr-enriched phase having a face-centered cubic structure in the copper alloy, and the proportion of a Cr phase having a body-centered cubic structure precipitated from the Cr-enriched phase, within a predetermined range, the Cr solid solubility and elastic strain in the copper matrix can be suppressed, resulting in a copper alloy powder that can realize an additively manufactured product with excellent electrical conductivity and a high relative density. The present invention is based on this discovery. The gist of the present invention is as follows.

[0008] [1] A copper alloy powder for additive manufacturing, containing Cr, with the remainder being Cu and unavoidable impurities, and having the following formula: R = A ｆ / A ｂ (In the formula, A ｆ represents an X-ray absorption spectrum derived from Cr having a face-centered cubic structure in a spectrum obtained by X-ray absorption near edge structure (XANES) analysis of the copper alloy powder, and A ｂ represents an X-ray absorption spectrum derived from Cr having a body-centered cubic structure obtained by XANES analysis of the copper alloy powder, ｂ and A ｆ The spectrum obtained is based on the spectrum of the standard sample. ２ O ３The linear coefficients of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure and the X-ray absorption spectrum derived from Cr having a face-centered cubic structure are normalized based on the linear coefficients of each spectrum when decomposed into a linear combination of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure, the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, and the X-ray absorption spectrum derived from Cr having a body-centered cubic structure.) is 0.1 to 10. [2] The copper alloy powder for additive manufacturing according to [1], having an oxygen concentration of 500 ppm or less by mass. [3] The copper alloy powder for additive manufacturing according to [1] or [2], having an angle of repose of 30° or more. [4] The copper alloy powder for additive manufacturing according to any of [1] to [3], having an a* value of the L*a*b* color system of 15 or more. [5] The copper alloy powder for additive manufacturing according to any one of [1] to [4], having an average particle size (D50) of 10 μm or more and 50 μm or less. [6] The copper alloy powder for additive manufacturing according to any one of [1] to [5], further containing Zr. [7] A method for producing an additively manufactured object using the copper alloy powder according to any one of [1] to [6], comprising: a first step of forming a powder layer containing the copper alloy powder; and a second step of forming a manufacturing layer by solidifying the copper alloy powder at a predetermined position in the powder layer, wherein the first step and the second step are sequentially repeated to stack the manufacturing layers, thereby producing an additively manufactured object. [8] The method according to [7], wherein the solidification of the copper alloy powder in the second step is performed by energy irradiation means selected from the group consisting of a laser, an electron beam, and plasma. [9] A method for producing a copper alloy product from an additive manufacturing method obtained by the method according to [7], the method comprising heat-treating the additive manufacturing method.

[10] The method according to [9], wherein the heat treatment is carried out at a temperature of 400°C or higher and lower than the melting point of the copper alloy.

[0009] According to the copper alloy powder for additive manufacturing of the present invention, additive manufacturing products having excellent electrical conductivity and high relative density can be obtained.

[0010] [Copper alloy powder] The copper alloy powder according to the present invention is used as a raw material powder in an additive manufacturing method. In the additive manufacturing method, the raw material powder is irradiated with an energy beam, whereby the raw material powder melts and is rapidly cooled and solidified. That is, the raw material powder is solidified by irradiation with the energy beam. Details of the additive manufacturing method will be described later in the section "Method for manufacturing an additive manufactured product."

[0011] The copper alloy powder according to one embodiment of the present invention contains Cr, with the balance being Cu and unavoidable impurities, and has a composition represented by the following formula: R = A ｆ / A ｂ The ratio R is 0.1 to 10. ｆ represents an X-ray absorption spectrum derived from Cr having a face-centered cubic structure in a spectrum obtained by X-ray absorption near edge structure (XANES) analysis of the copper alloy powder, and A ｂ represents the X-ray absorption spectrum derived from Cr having a body-centered cubic structure obtained by XANES analysis of the copper alloy powder. ｂ and A ｆ The spectrum obtained is based on the spectrum of the standard sample. ２ O ３ The linear coefficients of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure and the X-ray absorption spectrum derived from Cr having a face-centered cubic structure are normalized based on the linear coefficients of each spectrum when decomposed into a linear combination of the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, and the X-ray absorption spectrum derived from Cr having a body-centered cubic structure. The standard samples used were copper foil made of copper having a face-centered cubic structure (standard sample owned by Photon Factory BL-12C of the High Energy Accelerator Research Organization), chromium foil made of chromium having a body-centered cubic structure (same as above), α-Cr ２ O ３ (National Institute of Standards and Technology SRM674a) is used. ２ O ３ For the above A, boron nitride (manufactured by Kojundo Chemical Co., Ltd., purity 99%, BBI03PB) is used as a molding agent for molding the sample. ｆrepresents the X-ray absorption spectrum of Cr having a face-centered cubic structure, while A ｆ The reason why copper foil was used instead of chromium foil as the standard sample for determining α-Cr is that chromium does not have a stable face-centered cubic crystal phase, so the XANES spectrum of copper was used instead. The linear coefficients of each spectrum were calculated using XANES analysis software (Athena) under the following fitting conditions. <Fitting conditions> Standards: α-Cr ２ O ３ , copper foil (energy axis adjusted), chrome foil Fitting Space: norm μ (E) Energy range: -10 to 60 eV Fit E0: False Required: False All weights between 0 and 1: yes Force weights sum to 1: yes Overall e0 shift used: no Noise added to data: 0

[0012] The copper alloy powder of the present invention can improve the conductivity and relative density of an additive manufacturing product obtained by the L-PBF method using the copper alloy powder by adjusting the ratio of Cr dissolved in copper or a Cr-enriched phase having a face-centered cubic structure in the copper alloy and the ratio of the Cr phase having a body-centered cubic structure precipitated from the Cr-enriched phase (i.e., the ratio R) within a predetermined range. If the ratio R is less than 0.1, the additive manufacturing product obtained will have excellent conductivity but will not have a high relative density. On the other hand, if the ratio R exceeds 10, an additive manufacturing product with a high relative density will be obtained but will not have a high conductivity. The reason for this is unclear, but is thought to be as follows. That is, as described below, Cr-containing copper alloy powder prepared by an atomization method or the like will have Cr dissolved in copper or a Cr-enriched phase having a face-centered cubic structure in copper immediately after preparation. As a result, the elastic strain introduced by the dissolved Cr atoms and the elastically constrained face-centered cubic Cr-enriched phase acts as a scattering factor for free electrons, reducing the electronic and thermal conductivity of the copper alloy powder. Therefore, it is believed that the L-PBF method efficiently transfers thermal energy from the energy beam to the copper alloy powder, and suppresses the diffusion of heat from the molten raw material powder to the surroundings, resulting in an additive manufacturing product with a high relative density. Subsequent heat treatment reduces the Cr solid solubility and elastic strain in the copper matrix by precipitating Cr with a body-centered cubic structure, thereby improving the electronic conductivity of the copper matrix. As a result, it is believed that an additive manufacturing product with excellent electrical conductivity and high relative density can be obtained. The above-mentioned ratio R(A ｆ / A ｂ ) is preferably 0.2 to 7, more preferably 0.4 to 4.

[0013] The oxygen concentration of the copper alloy powder is preferably 500 ppm or less by mass, more preferably 400 ppm or less. When the oxygen concentration in the copper alloy powder is high, the proportion of copper oxide in the copper alloy increases, and the properties inherent to copper (such as high electrical and thermal conductivity) tend to decrease. The oxygen concentration can be calculated by oxygen gas analysis or the like. A method for adjusting the oxygen concentration of the copper alloy powder will be described later.

[0014] Furthermore, the copper alloy powder preferably has an angle of repose of 25° or more, more preferably 30° or more. When the angle of repose of the copper alloy powder is 25° or more, copper alloy powder particles contact each other over a large area, and also over a very small area. This allows the fluidity of the copper alloy powder to be appropriately suppressed when forming a powder bed using a coater or the like, thereby improving the packing properties of the powder bed. As a result, the relative density of the additive manufacturing product can be improved. The angle of repose can be adjusted by the physical properties (e.g., oxygen concentration) and shape (particle size and particle shape) of the copper alloy powder. The angle of repose refers to the angle between the floor and the slope of the mound formed by the copper alloy powder on a pedestal when the copper alloy powder is allowed to fall freely from a funnel. The angle of repose is an index of the fluidity of the copper alloy powder, and a smaller angle indicates better fluidity. However, if the fluidity is too high, the ease of forming a powder bed tends to decrease.

[0015] Furthermore, from the viewpoint of obtaining a fine and dense additive manufacturing product and from the viewpoint of the fluidity of the copper alloy powder, the average particle size of the copper alloy powder used is preferably 1 μm or more and 500 μm or less, more preferably 5 μm or more and 200 μm or less, and particularly preferably 10 μm or more and 50 μm or less. By using a copper alloy powder having an average particle size within the above range, it is possible to form a powder bed with a high packing density in a metal additive manufacturing method such as the L-PBF method, and it is also possible to increase the relative density of the molded product obtained by sintering or melt-solidifying the copper alloy powder. In this specification, the average particle size refers to the particle size (D ５０ ) is shown.

[0016] Furthermore, the shape of each particle constituting the copper alloy powder is not particularly limited, but when used in a metal additive manufacturing method such as the L-PBF method, it is preferable that each particle has a nearly spherical shape from the viewpoint of forming a powder bed with a high packing density of the copper alloy powder by squeegeeing. A method for obtaining such a copper alloy powder with a predetermined particle size that is nearly spherical will be described later.

[0017] The Cr content of the copper alloy powder is preferably 0.5% by mass or more and 5.0% by mass or less, more preferably 0.5% by mass or more and 3.1% by mass or less, and even more preferably 0.5% by mass or more and 2.5% by mass or less. The Cr content of the copper alloy powder can be measured by ICP atomic emission spectrometry (inductively coupled plasma atomic emission spectrometry) in accordance with JIS H 1071 (Method for determining chromium in copper and copper alloys). Specifically, a melt is first prepared by alkali melting treatment of the copper alloy, and a solution is prepared by acid dissolution treatment of the melt. The measurement sample is prepared by diluting the solution. Alternatively, a solution may be prepared directly by acid dissolution treatment of the copper alloy. The measurement sample can be prepared by diluting the solution.

[0018] The copper alloy powder of the present invention may contain inevitable impurity elements other than the above-mentioned components, or may contain elements intentionally added during the production of the copper alloy powder. For example, inevitable impurity elements such as oxygen, phosphorus, and iron, as well as elements such as nickel, zinc, tin, silver, beryllium, zirconium, aluminum, silicon, cobalt, titanium, magnesium, and tellurium may be contained. Among these, zirconium (Zr) is preferably contained. When the copper alloy powder contains Zr, its content is not particularly limited, but is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 1% by mass or less. The Zr content in the copper alloy powder can be measured in the same manner as the Cr content described above.

[0019] Furthermore, the copper alloy powder of the present invention preferably has an a* value of 15 or more in the L*a*b* color system (CIE 1976 L*a*b* color space). The L*a*b* value can be measured using a spectrophotometer. The a* value is an index representing hue and saturation, with a positive a* value indicating a reddish color and a negative a* value indicating a greenish color. The further the value is from the center (a* = 0), the more vivid the color, and the closer it is to the center, the duller the color. In the present invention, by using a copper alloy powder having an a* value of 15 or more, the laser light absorption efficiency of the copper alloy powder is improved when manufacturing an additive manufacturing product using the L-PBF method, resulting in an additive manufacturing product with a higher relative density. The L*a*b* value of the copper alloy powder can be measured using a commercially available colorimeter in accordance with JIS Z 8722.

[0020] [Method for Producing Copper Alloy Powder] Next, a method for producing the above-mentioned copper alloy powder will be described. Copper alloy powder is generally produced by, for example, gas atomization, water atomization, disk atomization, plasma atomization, rotating electrode atomization, etc. However, in an embodiment of the present invention, copper alloy powder is produced by gas atomization from a molten copper alloy (i.e., a molten raw material in which copper is mixed with a predetermined Cr, etc.). The gas atomization method is a method in which a molten raw material prepared to have a desired composition is heated to or above its melting point by high-frequency induction heating, and the molten metal flows out through fine holes. An inert gas such as argon gas or nitrogen gas is sprayed onto the molten metal to finely pulverize it, and the molten metal is rapidly cooled and solidified to obtain powder.

[0021] Next, the copper alloy powder obtained by gas atomization is classified to adjust it to a predetermined aspect ratio and a predetermined uniformity. The classification of the copper alloy powder is preferably carried out in two stages, with the removal of large diameter particles and the removal of small diameter particles separately. When the classification of the copper alloy powder is carried out in two stages, the order of classification is not particularly limited, and either the large diameter particles or the small diameter particles can be removed in the first stage, and the other can be removed in the second stage. In a preferred embodiment of the present invention, from the viewpoint of performing classification more efficiently, it is preferable to first remove the large diameter particles in the first stage and then remove the small diameter particles in the second stage.

[0022] Next, the copper alloy powder whose particle size has been adjusted as described above is preferably dried at a temperature of about 50 to 100°C. By carrying out such a drying step, the properties of the copper alloy powder are stabilized. Note that, since drying in an air atmosphere may cause oxidation of the copper alloy powder, it is preferable to carry out the drying in an inert atmosphere such as nitrogen or argon. For example, the copper alloy powder can be dried at 60°C for about 3 hours.

[0023] In the present invention, the copper alloy powder dried as described above can be used as it is as a copper alloy powder for an additive manufacturing product, but it may also be subjected to a heat treatment. The ratio of Cr having a face-centered cubic structure to Cr having a body-centered cubic structure in the copper alloy powder can also be adjusted by the heat treatment. That is, the ratio R(A ｆ / A ｂ ) can be adjusted.

[0024] When heat treating copper alloy powder, it is preferable to do so at a temperature below 500°C. If heat treatment is performed at a temperature of 500°C or higher, the proportion of Cr having a body-centered cubic structure becomes too high, making it difficult to achieve a ratio R of 0.1 or more. The heat treatment time may also be adjusted as appropriate, but is preferably about 1 to 10 hours, and more preferably 2 to 5 hours. If the heat treatment time is too long, the proportion of Cr having a body-centered cubic structure becomes too high, as described above, making it difficult to achieve a ratio R of 0.1 or more. For example, heat treatment can be performed at a temperature of 100°C to 400°C for about 2 to 4 hours.

[0025] [Method for Manufacturing an Additively Manufactured Product] Next, a method for manufacturing an additively shaped product using the metal powder described above will be described. The additively shaped product can be manufactured by forming a powder layer containing metal powder (first step), solidifying the metal powder at a predetermined position in the powder layer to form a modeling layer (second step), and sequentially repeating the first and second steps to stack the modeling layers. Specific embodiments will be described below. This description will be given of an embodiment in which a laser is used in powder bed fusion as a means for solidifying the metal powder. However, this means is not limited to a laser as long as it is capable of solidifying the metal powder. The means may also be, for example, an electron beam or plasma. In this embodiment, additive manufacturing (AM) methods other than powder bed fusion may also be used. In this embodiment, for example, directed energy deposition, binder jetting, fused deposition modeling, cold spraying, etc. may also be used. Furthermore, in this embodiment, cutting may be performed during the manufacturing process.

[0026] An additive manufacturing object can be manufactured by an additive manufacturing device. For example, three-dimensional shape data is created by a 3D scanner or the like. The three-dimensional shape data is, so to speak, a design drawing of the additive manufacturing object. The three-dimensional shape data is sliced ​​at predetermined intervals to create slice data. The slice interval is also referred to as a slice thickness. The slice data is, so to speak, a design drawing of the manufacturing layers.

[0027] An additive manufacturing apparatus is also called a "3D printer" and generally comprises a piston, a table, and an output unit. The piston supports the table. The piston can move up and down.

[0028] The piston lowers the table. The amount of lowering corresponds to one layer of the slice data. Metal powder is laid on the table using a coater (blade, spatula, brush, roller, etc.). This forms a powder bed. When the powder bed is laid, the coater smooths the surface and removes excess metal powder. The powder bed contains metal powder. For example, the powder bed may consist essentially of metal powder. The coater's movement speed when forming the powder bed is preferably 10 mm / sec or more and 800 mm / sec or less, more preferably 10 mm / sec or more and 500 mm / sec or less, and particularly preferably 10 mm / sec or more and 150 mm / sec or less. The metal powder of the present invention has high fluidity and packing ability, so a powder bed of uniform thickness can be formed even when the coater's movement speed is relatively high. The thickness of the powder bed to be formed is preferably 0.01 mm or more and 0.5 mm or less, more preferably 0.01 mm or more and 0.2 mm or less, and particularly preferably 0.01 mm or more and 0.07 mm or less, from the viewpoint of being able to form a powder bed of uniform thickness with a coater.

[0029] The output unit of the additive manufacturing device irradiates an energy beam onto the powder bed (metal powder). The energy beam scans the powder bed in a predetermined pattern. The scanning pattern follows the slice data. The metal powder irradiated with the energy beam melts and then rapidly cools and solidifies or sinters. In other words, the metal powder irradiated with the energy beam solidifies. A modeling layer is formed according to the scanning pattern of the energy beam. The modeling layer is also called a solidified layer, solidified layer, sintered layer, unit layer, etc. Note that "solidification" refers to the loss of fluidity of the metal particle group as the metal particle group fuses and becomes one.

[0030] The energy beam may include at least one selected from the group consisting of a laser, an electron beam, and plasma. The energy beam may include, for example, a Yb fiber laser, a YAG laser, a CO２ The energy beam may include at least one selected from the group consisting of a laser, a semiconductor laser, a blue laser, and a green laser. The output of the energy beam may be, for example, 20 to 10,000 W. The scanning speed of the energy beam may be, for example, 50 to 10,000 mm / s. The energy density of the energy beam may be, for example, 40 to 1,000 J / mm ３ and preferably 60 to 800 J / mm ３ , more preferably 80 to 600 J / mm ３ The metal powder of the present invention has high fluidity and packing properties, so that a powder bed of high density and uniform thickness can be formed by squeegeeing (i.e., a powder bed with excellent thermal conductivity can be formed). Therefore, when irradiating the powder bed with an energy beam, even if the pitch interval when scanning the energy beam is widened or the scanning speed is increased, the powder bed can be properly solidified, and as a result, the energy density can be reduced.

[0031] After forming the first modeling layer in this manner, the piston lowers the table again. The amount of lowering corresponds to one layer of slice data. As described above, a second modeling layer is further formed, and the formation of the modeling layer is repeated to construct a layered object. In other words, a layered object can be manufactured by stacking multiple modeling layers.

[0032] For example, the layered object may be manufactured in an inert gas atmosphere. By manufacturing the layered object in an inert gas atmosphere, it is expected that oxidation of the layered object can be suppressed. The inert gas may be, for example, argon (Ar), nitrogen (N ２ ), and helium (He). For example, the layered object may be manufactured in a reducing gas atmosphere. The reducing gas may include, for example, hydrogen (H ２ For example, the layered object may be manufactured in a reduced pressure atmosphere.

[0033] The additively manufactured object may have any shape. For example, it may have a seamless and complex internal structure. For example, it is considered difficult to form a seamless and complex internal structure by machining.

[0034] [Copper Alloy Molded Product] The additively manufactured product obtained as described above has improved electrical conductivity when subjected to heat treatment. In the present invention, the additively manufactured product is made using a copper alloy powder containing a predetermined amount of chromium and a specific element in a predetermined ratio. Therefore, the copper alloy molded product obtained by heat treatment at 400°C or higher has excellent electrical conductivity while maintaining mechanical strength. The heat treatment can be carried out using a heat treatment furnace or the like. The heat treatment temperature can be measured using a temperature sensor or the like attached to the heat treatment furnace. For example, if the set temperature of the heat treatment furnace is 300°C, the heat treatment temperature can be considered to be 300°C.

[0035] The heat treatment must be performed at a temperature below the melting point of the copper alloy, but may be, for example, 900°C or lower. By setting the heat treatment temperature to 900°C or lower, it is expected that the electrical conductivity will be improved while suppressing excessive softening. The heat treatment temperature is more preferably 800°C or lower, and more preferably 700°C or lower. On the other hand, from the viewpoint of improving mechanical strength while maintaining good electrical conductivity, the lower limit of the heat treatment temperature is preferably 400°C or higher, and more preferably 550°C or higher. The heat treatment temperature may be changed during the heat treatment process. For example, the temperature may be increased from room temperature to 700°C, held at 700°C for 1 hour, decreased from 700°C to 500°C, held at 500°C for 5 hours, and then decreased from 500°C to room temperature.

[0036] For example, the time may be 0.1 to 100 hours, 0.5 to 50 hours, or 1 to 40 hours. The atmosphere inside the heat treatment furnace may be, for example, a nitrogen atmosphere, an argon atmosphere, a hydrogen atmosphere, a reduced pressure atmosphere, or the like.

[0037] A copper alloy molded product obtained by heat-treating an additive manufacturing product may have, for example, a conductivity of 50% IACS or more. It preferably has a conductivity of 75% IACS or more, and more preferably 90% IACS or more. Note that "conductivity" refers to IACS conductivity. That is, the conductivity of annealed standard soft copper (International Annealed Copper Standard, IACS) is defined as 100% IACS. The conductivity is measured using an eddy current conductivity meter. The measurement temperature is room temperature (15 to 25°C).

[0038] The additively manufactured object and the copper alloy molded object are made of a copper alloy. The copper alloy may have high electrical conductivity and high thermal conductivity. The additively manufactured object may be used in applications where the properties of the copper alloy are utilized. The additively manufactured object may be used, for example, in induction heating coils, heat sinks, rocket engines, etc. In the additively manufactured object, complex water cooling paths (internal structures) can be realized without joints.

[0039] The additively manufactured product and copper alloy molded product according to one embodiment of the present invention may have a relative density of, for example, 99% or more. The relative density of the copper alloy molded product may be substantially the same as the relative density of the additively manufactured product before heat treatment. The relative density is expressed as a percentage of the measured density relative to the theoretical density. Here, "theoretical density" is defined as the density of an ingot material having substantially the same alloy composition as the alloy composition of the measurement target (additively manufactured product). The measured density may be measured in accordance with "JIS Z 2501 Sintered Metal Materials - Test Method for Density, Oil Content, and Open Porosity." When measuring the measured density, water is used as a replacement liquid.

[0040] Next, the embodiments of the present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0041] <Preparation of Copper Alloy Powder> A copper alloy containing 1.0 mass% Cr and the remainder copper was melted and gas atomized to obtain a copper alloy powder. The obtained copper alloy powder was first classified using a vibrating sieve with a 45 μm mesh to remove large-diameter particles and recover the small-diameter powder. The powder was then dried at 60°C for 30 minutes to obtain the target copper alloy powder. The copper alloy powder thus obtained is referred to as Cu—Cr. A copper alloy containing 0.88 mass% Cr, 0.06 mass% Zr, and the remainder copper was melted and gas atomized to obtain a copper alloy powder. The obtained copper alloy powder was first classified using a vibrating sieve with a 45 μm mesh to remove large-diameter particles and recover the small-diameter powder. The powder was then dried at 60°C for 30 minutes to obtain the target copper alloy powder. The copper alloy powder thus obtained is referred to as Cu—Cr—Zr.

[0042] Subsequently, each of the obtained copper alloy powders was subjected to a heat treatment under the conditions (temperature, time) shown in Table 1 below.

[0043] <Acquisition of XANES Spectra> Acquisition of Cr-K shell X-ray absorption near-edge structure spectra (hereinafter also referred to as Cu-K shell XANES spectra) for each of the obtained copper alloy powders was carried out by a fluorescence method using beamline BL-12C of the Photon Factory (synchrotron energy: 2.5 GeV) and beamline BL5S1 of Aichi SR (synchrotron energy: 1.2 GeV). The analysis was carried out in the atmosphere using a silicon drift detector (SDD) with a Si(111) crystal in the energy range of 5690 eV to 6692 eV. Furthermore, as standard samples, copper foil made of copper with a face-centered cubic structure (standard sample owned by the High Energy Accelerator Research Organization Photon Factory BL-12C), chromium foil made of chromium with a body-centered cubic structure (same as above), α-Cr ２ O ３ (National Institute of Standards and Technology SRM674a) was used. ２ O ３ The samples were prepared in the following manner: First, α-Cr ２ O ３ and boron nitride (purity 99%, BBI03PB, manufactured by Kojundo Chemical Co., Ltd.) in a mass ratio of α-Cr２ O ３ The powders were weighed so that the ratio of α-Cr to α-Cr was 1:48, and mixed in a mortar for 20 minutes or more. Then, 120 mg of the mixed powder was placed in a mold with a diameter of 10 mm and compressed with a hand press to form a pellet. The XANES spectra of these standard samples were obtained by the transmission method. ２ O ３ The energy range of the Cr-K-edge XANES spectrum is the same as that of each copper alloy powder. For the copper foil, the Cu-K-edge XANES spectrum was acquired in the energy range of 8475 eV to 10117 eV.

[0044] <Analysis of XANES Spectra> First, the energy axis of the Cu-K-shell XANES spectrum obtained from the copper foil was adjusted to the Cr-K-shell in order to use it in the analysis of the Cr-K-shell XANES spectrum. Specifically, the Cu-K-shell XANES spectrum of the copper foil read by Athena was saved as an .xmu file, and the value of "# Element.symbol:" was changed from Cu to Cr and the value of "# Athena.e0:" was changed to 5993.84 eV using text editing software, and the file was then saved. Next, the Cu-K-shell XANES spectrum of the copper foil with the energy axis changed as described above, as well as the Cu-K-shell XANES spectrum of each copper powder alloy powder, chromium foil, and α-Cr ２ O ３ Each Cr-K edge XANES spectrum was normalized using the software Athena under the following conditions: Pre-edge range: -150 to -30 eV Normalization range: 105 to 605 eV

[0045] Next, the Linear Combination Fitting page of the software Athena was opened, and linear fitting was performed with the following settings. Note that the software Athena used was version 0.9.26. <Fitting Conditions> Standards: α-Cr ２ O ３, copper foil (energy axis adjusted), chrome foil Fitting Space: norm μ (E) Energy range: -10 to 60 eV Fit E0: False Required: False All weights between 0 and 1: yes Force weights sum to 1: yes Overall e0 shift used: no Noise added to data: 0

[0046] From the fitting results, for each copper alloy powder, ｂ and A ｆ The results are shown in Table 1. ｂ and A ｆ The spectrum obtained is based on the spectrum of the standard sample. ２ O ３ The linear coefficients of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure and the X-ray absorption spectrum derived from Cr having a face-centered cubic structure are normalized based on the linear coefficients of each spectrum when the X-ray absorption spectrum derived from Cr having a face-centered cubic structure and the X-ray absorption spectrum derived from Cr having a body-centered cubic structure are decomposed into a linear combination of the X-ray absorption spectrum derived from Cr having a face-centered cubic structure. ２ O ３ The linear coefficient of the X-ray absorption spectrum derived from ２ O ３ the value of ), the linear coefficient of the X-ray absorption spectrum originating from Cr having a face-centered cubic structure (A in Table 1) ｆ ) and the linear coefficient of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure (A in Table 1). ｂ The values ​​were normalized so that the sum of the values ​​was 1.

[0047] <Measurement of particle size of copper alloy powder> For each copper alloy powder obtained as described above, a laser diffraction particle size distribution analyzer (MT-3300EX-II, manufactured by Microtrac) was used to measure the particle size (dmin) corresponding to an integrated frequency of 0 volume %, the particle size (d10) corresponding to an integrated frequency of 10 volume %, the particle size (d50) corresponding to an integrated frequency of 50 volume %, and the particle size (d90) corresponding to an integrated frequency of 90 volume %. The measurement results are shown in Table 1 below.

[0048] <Oxygen Concentration> The oxygen content of each copper alloy powder obtained as described above was measured using an oxygen / nitrogen analyzer (EMGA-620, Horiba, Ltd.). The oxygen content was determined by measuring the amount of CO, CO2, and CO2 generated when the metal powder was heated and melted in a He atmosphere. ２ The measurement results are shown in Table 1 below.

[0049] <Angle of repose> The angle of repose of each copper alloy powder obtained as described above was measured. The angle of repose was measured using a multifunctional powder property measuring instrument (MT-1001, manufactured by Seishin Enterprise Co., Ltd.) by placing the copper alloy powder through a sieve (JIS standard Z8801-1-2000, mesh size 75 μm). The measurement results are shown in Table 1 below.

[0050] <Measurement of L* Value, a* Value, and b* Value> The L* value, a* value, and b* value of each copper alloy powder obtained as described above were measured using a colorimeter (ZE 6000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS Z 8722. The measurement results are shown in Table 1 below.

[0051] <Production of Layer-by-Layer-Modeled Objects> Layer-by-layer-modeled objects were produced for each copper alloy powder using an layer-by-layer-modeling device (EOS M290, manufactured by EOS Electro Optical Systems Japan Co., Ltd.) under the following production conditions. Prismatic test pieces (10 mm square bottom x 15 mm height) were produced as layer-by-layer-modeled objects. Production conditions: Laser type: fiber laser, 370 W Spot diameter: approximately 0.1 mm Laser irradiation speed: 600 mm / s Layer thickness: 0.03 mm

[0052] <Production of Copper Alloy Product> The layered product obtained as described above was placed in a heat treatment furnace and subjected to heat treatment at 700° C. for 3 hours in a nitrogen atmosphere to obtain a copper alloy product.

[0053] <Measurement of Electrical Conductivity> The electrical conductivity of the copper alloy formed as described above was measured using an eddy current type conductivity meter. The measurement results are shown in Table 1 below.

[0054] <Measurement of relative density> The theoretical density of the copper alloy formed product obtained as described above was calculated, and the actual density was measured in accordance with JIS Z 2501 "Sintered metal materials - Test method for density, oil content and open porosity." The relative density was calculated from the obtained theoretical density and the actual density. The theoretical density was calculated by multiplying the densities of general Cu, Cr, and Zr by their respective content ratios and adding them up. The calculation results are shown in Table 1 below.

[0055]

[0056] As is clear from Table 1, it can be seen that an additive manufacturing product (copper alloy product) having excellent conductivity and high relative density can be obtained with copper alloy powders in which the ratio R of the X-ray absorption spectrum derived from Cr having a face-centered cubic structure to the X-ray absorption spectrum derived from Cr having a body-centered cubic structure of the copper alloy powder is in the range of 0.1 to 10. On the other hand, it can be seen that with copper alloy powders in which the ratio R is less than 0.1, the obtained additive manufacturing product (copper alloy product) has excellent conductivity but does not have a relative density of more than 99%.

Claims

1. A copper alloy powder for additive manufacturing, containing Cr, with the remainder being Cu and unavoidable impurities, and having the following formula: R = A ｆ / A ｂ (In the formula, A ｆ represents an X-ray absorption spectrum derived from Cr having a face-centered cubic structure in a spectrum obtained by X-ray absorption near edge structure (XANES) analysis of the copper alloy powder, and A ｂ represents an X-ray absorption spectrum derived from Cr having a body-centered cubic structure obtained by XANES analysis of the copper alloy powder, ｂ and A ｆ The spectrum obtained is based on the spectrum of the standard sample. ２ O ３ The copper alloy powder for additive manufacturing has a ratio R of 0.1 to 10, which is obtained by normalizing the linear coefficients of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure and the X-ray absorption spectrum derived from Cr having a face-centered cubic structure based on the linear coefficients of each spectrum when decomposed into a linear combination of the X-ray absorption spectrum derived from Cr having a body-centered cubic structure, the X-ray absorption spectrum derived from Cr having a face-centered cubic structure, and the X-ray absorption spectrum derived from Cr having a body-centered cubic structure.

2. The copper alloy powder for additive manufacturing according to claim 1, wherein the oxygen concentration is 500 ppm or less by mass.

3. The copper alloy powder for additive manufacturing according to claim 2, having an angle of repose of 30° or more.

4. The copper alloy powder for additive manufacturing according to claim 1, wherein the a* value of the L*a*b* color system is 15 or more.

5. The copper alloy powder for additive manufacturing according to claim 1, having an average particle diameter (D50) of 10 μm or more and 50 μm or less.

6. The copper alloy powder for additive manufacturing according to claim 1, further containing Zr.

7. A method for manufacturing an additively manufactured object using the copper alloy powder according to claim 1, comprising: a first step of forming a powder layer containing the copper alloy powder; and a second step of forming a modeling layer by solidifying the copper alloy powder at a predetermined position in the powder layer, wherein the first step and the second step are repeated in sequence to manufacture the additively manufactured object by stacking the modeling layers.

8. The method according to claim 7, wherein the consolidation of the copper alloy powder in the second step is carried out by an energy irradiation means selected from the group consisting of a laser, an electron beam, and plasma.

9. A method for producing a copper alloy product from an additively shaped product obtained by the method according to claim 7, comprising heat treating the additively shaped product.

10. The method of claim 9, wherein the heat treatment is carried out at a temperature of 400°C or higher and below the melting point of the copper alloy.

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