Methods for manufacturing alloy materials and their applications
By forming a W-Cu alloy through an oxidizing and reducing treatment, the method addresses the weakness of conventional W-Cu joints, providing strong and reliable bonding for high-temperature applications.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- NORITAKE MACHINE TECHNO CO LTD
- Filing Date
- 2024-09-13
- Publication Date
- 2026-07-17
AI Technical Summary
Conventional joining methods for tungsten (W) and copper (Cu) members fail to achieve strong and reliable joints due to the lack of interdiffusion between these metals, limiting their application in high-temperature environments.
A manufacturing method involving the formation of an oxidizing contact between W and Cu sources, followed by a reducing atmosphere treatment, results in the creation of a W-Cu alloy at their interface, enabling strong and reliable bonding.
The method produces a W-Cu alloy with sufficient thickness for robust joint formation, enhancing the bonding strength and reliability of W members with other metals, suitable for high-temperature components.
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing an alloy material and various members obtained by the manufacturing method.
Background Art
[0002] A tungsten member (hereinafter also referred to as "W member") containing tungsten (W) has characteristics of a high melting point and a low thermal expansion coefficient, and is excellent in reliability in a high-temperature environment. For this reason, the W member is used for ultra-high temperature parts exposed to a high-temperature environment such as a divertor, an accelerator, a plasma discharge device, a high-temperature furnace, and a thin film forming device. On the other hand, tungsten is a rare and expensive metal, and is difficult to process. For this reason, a metal bonded body in which a W member and another metal member are bonded is widely used. As an example of a bonding target of such a W member, a member made of copper (Cu) (hereinafter also referred to as "Cu member") can be mentioned.
[0003] However, according to the Inorganic Material Database (AtomWork) by the National Institute for Materials Science and the like, it is said that an alloy in which metal elements diffuse mutually does not occur between a W member and a Cu member. That is, in the joining of the W member and the Cu member, it is considered that a joining means of forming a strong joining part by generating an alloy at the boundary of the two metal members cannot be used, and joining means other than the generation of the alloy are acting. As an example of such other joining means, there is a means of heating while pressing the W member and the Cu member with a strong pressure. In the joined body produced by such a means, it is considered that an intermetallic bond has occurred in a very thin region at the joining interface between the W member and the Cu member. Further, Patent Document 1 describes a method for manufacturing a dissimilar metal joined body in which a W member and a Cu member are joined. In this manufacturing method, after interposing copper powder between a copper-containing bulk material (Cu member) and a tungsten-containing material (W member), spark plasma sintering treatment is performed in a predetermined atmosphere. Patent Document 1 describes that a dissimilar metal joined body excellent in joining strength and suppressing the occurrence of various problems can be manufactured by the above-described joining means (manufacturing method).
Prior Art Documents
[0004] [Patent Document 1] Patent No. 6563581 [Overview of the Initiative] [Problems that the invention aims to solve]
[0005] In recent years, with the expanding applications of W members, there has been a demand for even greater joint strength and reliability in metal joints formed by joining W members to other metal members (e.g., Cu members). However, conventional joining methods described above have made it difficult to achieve a strong and reliable joint that meets recent demands. The present invention was made to solve the above problem, and its main objective is to provide a novel technology that enables a strong and reliable joint between tungsten members and other metal members. [Means for solving the problem]
[0006] To solve the above-mentioned problems, the inventors conducted various experiments and studies and discovered that when an oxidizing contact body, in which a W source and a Cu source containing Cu elements are in contact, and W oxide and Cu oxide exist at the boundary between the W source and Cu source, is subjected to a firing treatment under a reducing atmosphere, a surprising alloy material (W-Cu alloy) is produced in which the W and Cu elements, which were previously thought not to interdiffuse, mutually diffuse. The inventors then considered that by using this W-Cu alloy, it would be possible to join W members to other metal members via the alloy material, thereby enabling the creation of a strong and highly reliable metal joint.
[0007] The method for manufacturing alloy materials disclosed herein (hereinafter also simply referred to as the "manufacturing method") is based on the above-mentioned knowledge. Specifically, the manufacturing method disclosed herein prepares an oxidizing contact body in which a W source containing tungsten (W) and a Cu source containing copper (Cu) are in contact, and W and Cu are oxidized at the boundary between the W source and the Cu source, and the oxidizing contact body is subjected to a firing treatment under a reducing atmosphere. This makes it possible to form a W-Cu alloy in which W and Cu elements are interdiffused. Then, by joining a W member and a Cu member via this W-Cu alloy, a strong and reliable metal joint can be produced.
[0008] In one embodiment of the manufacturing method disclosed herein, the W source is a solid metal member containing the element W (W member). By using the W member in this way as the W source, a W-Cu alloy can be formed on the surface of the W member. A metal laminate in which the W-Cu alloy is formed on the surface of the W member in this way can be suitably used when manufacturing a metal composite in which the W member is joined to other metal members.
[0009] In one embodiment of the manufacturing method disclosed herein, the W source includes at least one selected from the group consisting of tungsten, tungsten nitride, tungsten carbide, tungsten carbonitride, copper-tungsten composite material, and silver-tungsten composite material. By using the above-mentioned W-based material as the W source, a W-Cu alloy can be appropriately formed.
[0010] In one embodiment of the manufacturing method disclosed herein, the Cu source is a Cu powder substantially composed of copper particles containing the copper element. By using such a powder Cu source, interdiffusion between the W element and the Cu element is facilitated, thereby improving the manufacturing efficiency of the W-Cu alloy.
[0011] In the embodiment using the above Cu powder, it is preferable that the Cu powder has an average particle size of 10 nm to 5000 nm based on SEM observation. By using such extremely fine Cu powder, interdiffusion between W element and Cu element is further facilitated, allowing for more efficient production of W-Cu alloy.
[0012] In one embodiment of the manufacturing method disclosed herein, the Cu source is a Cu paste obtained by dispersing Cu powder in a predetermined solvent. This facilitates contact between the W source and the Cu source, thereby further improving the manufacturing efficiency of the W-Cu alloy. Furthermore, when the W source is a W component, it is possible to prevent the formation of voids between the manufactured W-Cu alloy and the W component.
[0013] In one embodiment of the manufacturing method disclosed herein, an oxidized contact is prepared by performing an oxidation treatment on a contact body in which a W source and a Cu source are in contact. This makes it possible to easily obtain an oxidized contact. However, the manufacturing method disclosed herein is not limited to this embodiment, and an oxidized contact body may be prepared by bringing individually oxidized W sources and Cu sources into contact.
[0014] In the above-described oxidation treatment, after the oxidation treatment but before the firing treatment, copper oxide is present in a region of at least 5 nm from the surface of the Cu source in contact with the W source. By performing the oxidation treatment in such a way that copper oxide is present at a predetermined thickness from the surface of the Cu source, a W-Cu alloy with a certain thickness or more (typically 5 nm or more) can be produced more appropriately.
[0015] In the above-described oxidation treatment, after the oxidation treatment but before the firing treatment, tungsten oxide is present in a region of at least 5 nm from the surface of the W source in contact with the Cu source. By performing the oxidation treatment in such a way that tungsten oxide is present at a predetermined thickness from the surface of the W source, a W-Cu alloy of a certain thickness or more (typically 5 nm or more) can be produced more appropriately.
[0016] In the above-described oxidation treatment, the contacts are heated under an oxidizing atmosphere. This allows the W source and Cu source to be sufficiently oxidized in a short time, thus enabling the efficient production of W-Cu alloy.
[0017] In the above-described oxidation treatment, the heating temperature during the oxidation treatment is preferably 50°C or higher and 200°C or lower. By setting the heating temperature of the oxidation treatment to 50°C or higher, the W source and Cu source can be sufficiently oxidized in a shorter time. On the other hand, by setting the heating temperature of the oxidation treatment to 200°C or lower, it is possible to reliably prevent the W source and Cu source from sintering during the oxidation treatment, and to prevent excessive oxidation of the Cu source.
[0018] In the embodiment in which the above oxidation treatment is carried out, the heating time in the oxidation treatment is preferably 0.5 hours or more. This allows the W source and Cu source to be sufficiently oxidized, so that a W-Cu alloy can be properly manufactured.
[0019] In one embodiment of the manufacturing method disclosed herein, the firing process is carried out in an atmosphere filled with a mixed gas, which is a mixture of a neutral gas or an inert gas and a reducing gas. By mixing in a neutral gas (or an inert gas) in this way and reducing the concentration of the reducing gas, the reduction of copper oxide and the like in a low-temperature environment is suppressed, and the oxidized state can be maintained until the temperature is raised to a high-temperature environment, thereby improving the efficiency of W-Cu alloy production.
[0020] Furthermore, as mentioned above, when the firing process is carried out in an atmosphere filled with a mixed gas containing a reducing gas, the concentration of the reducing gas in the mixed gas is preferably 1% to 5%. By using a mixed gas with such a low concentration of reducing gas, the production efficiency of W-Cu alloy can be more effectively improved. Hydrogen gas is preferred as the reducing gas used in this process.
[0021] In one embodiment of the manufacturing method disclosed herein, the heating temperature in the sintering process is 500°C or higher and 1100°C or lower. By setting the heating temperature of the sintering process to 500°C or higher, the interdiffusion of W elements and Cu elements is promoted, and the manufacturing efficiency of W-Cu alloys can be improved. On the other hand, by setting the heating temperature of the sintering process to 1100°C or lower, it is possible to prevent the W source and Cu source from melting.
[0022] In one aspect of the manufacturing method disclosed herein, the heating time in the firing process is 0.1 hour or more. By this, sufficient mutual diffusion between the W element and the Cu element can occur, and a W-Cu alloy can be appropriately manufactured.
[0023] Also, as another aspect of the technology disclosed herein, an alloy material manufactured by the above-described manufacturing method is provided. This alloy material is a W-Cu alloy material containing, as a main component, a W-Cu alloy in which copper (Cu) elements and tungsten (W) elements are mutually dispersed. And according to the above-described manufacturing method, a W-Cu alloy material having a thickness of 5 nm or more can be manufactured. Such a W-Cu alloy material having a sufficient thickness is suitable as a bonding material for bonding a W member and another metal member.
[0024] Furthermore, as another aspect of the technology disclosed herein, a metal laminate provided with a W-Cu alloy layer can be mentioned. Such a metal laminate includes a W member containing a tungsten (W) element and a W-Cu alloy layer formed on the surface of the W member and containing, as a main component, a W-Cu alloy in which copper (Cu) elements and tungsten (W) elements are mutually dispersed. And in the metal laminate disclosed herein, the thickness of the W-Cu alloy layer is 5 nm or more. By using a metal laminate having such a configuration, a W member and another metal member can be bonded through a W-Cu alloy layer having a sufficient thickness, and a strong and highly reliable metal bonded body can be produced.
[0025] In addition, as another aspect of the technology disclosed herein, a metal bonded body is provided. Such a metal bonded body includes the above-described metal laminate and a bonding target bonded to the surface of the W-Cu alloy layer of the metal laminate. In such a metal bonded body, since the W member and another metal member are bonded through the W-Cu alloy layer, it is strong and has high reliability.
[0026] In one aspect of the bonded body disclosed herein, the bonding target is a Cu member containing a copper (Cu) element. Further, such a Cu member is preferably at least one selected from the group consisting of tough pitch copper, oxygen-free copper, copper alloy, and copper powder sintered body. The W-Cu alloy obtained by the technology disclosed herein can be particularly preferably bonded to the Cu member. In other words, the technology disclosed herein can be particularly preferably used for manufacturing a metal bonded body in which a W member and a Cu member are bonded.
Brief Description of Drawings
[0027] [Figure 1] (a) is a cross-sectional SEM image (100,000 times magnification) of Sample 1, and (b) and (c) are element maps of Cu and W based on EDX analysis, respectively. [Figure 2] (a) is a cross-sectional SEM image (100,000 times magnification) of Sample 2, and (b) and (c) are element maps of Cu and W based on EDX analysis, respectively. [Figure 3] It is a SEM photograph of Sample 2. [Figure 4] (a) is a cross-sectional SEM image (50,000 times magnification) of Sample 3, and (b) to (d) are element maps of O, Cu, and W based on EDX analysis, respectively.
Embodiments for Carrying Out the Invention
[0028] Hereinafter, an embodiment of the technology disclosed herein will be described. Matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and the common technical knowledge in the relevant field. In this specification, when it is described as "A to B (A and B are numerical values)", it means "A or more and B or less".
[0029] 1. Manufacturing Method of Alloy Material First, the method for manufacturing the alloy material disclosed herein will be described. In the manufacturing method disclosed herein, the oxidizing contact is subjected to a sintering treatment under a reducing atmosphere. This makes it possible to produce an alloy material (W-Cu alloy) in which W and Cu elements are mutually diffused. The following describes each step in this manufacturing method in detail.
[0030] (1) Preparation of the oxidizing contact In the manufacturing method disclosed herein, first, an oxidation contact is prepared. In this specification, "oxidation contact" refers to a contact in which a W source and a Cu source are in contact, and in which W oxide and Cu oxide are present at the boundary between the W source and the Cu source.
[0031] (a) W source The W source can be any material containing the element tungsten (W), and its form and specific composition are not particularly limited. For example, the form of the W source may be a solid metal member containing the element W (W member), or it may be a W powder substantially composed of tungsten particles containing the element W. Alternatively, the W source may be a W paste obtained by dispersing the W powder in a predetermined solvent. Among these forms, it is preferable to use a solid metal member, the W member, as the W source. This makes it possible to manufacture a metal laminate in which a W-Cu alloy is formed on the surface of the W member. This simplifies the procedure for joining the W member to other metal members (to be joined). Furthermore, when using W powder as the W source, the average particle size of the W powder is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less, and particularly preferably 1 μm or less. By using such fine W powder as the W source, the interdiffusion between the element W and the element Cu in the reduction firing treatment described later can be promoted. Furthermore, considering the ease of handling the W source when preparing the oxidation contact, the average particle size of the W powder is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 30 nm or more, and particularly preferably 50 nm or more. In this specification, "average particle size" is the arithmetic mean of the area circle equivalent diameter of 200 particles measured based on SEM observation or TEM observation. Also, when using W paste as the W source, the components other than W powder (solvent, binder, dispersant, etc.) are not particularly limited, and components that can be added to general metal pastes can be used without particular restriction.
[0032] Furthermore, examples of components of the W source include tungsten, tungsten nitride, tungsten carbide, and tungsten carbonitride. From the viewpoint of preventing poor formation of W-Cu alloys due to a deficiency of W element, it is preferable that the W source contains W element as its main component. Here, "containing W element as its main component" means that elements other than W element are not intentionally included. Therefore, if unavoidable impurities (metal elements other than W element) originating from raw materials or manufacturing processes are included in the W source, they are encompassed by the concept of "containing W element as its main component" in this specification. For example, if the total number of metal elements constituting the W source is 100 at%, then if the number of W element atoms is 75 at% or more, it can be said that it "contains W element as its main component." Furthermore, from the viewpoint of more appropriately facilitating the diffusion of W element during the firing process, the number of W element atoms in the W source is preferably 77.5 at% or more, more preferably 80 at% or more, even more preferably 82.5 at% or more, and particularly preferably 85 at% or more. Furthermore, the upper limit of the number of W atoms in the W source is not particularly limited and may be 99.5 at% or less, 97.5 at% or less, 95 at% or less, 92.5 at% or less, or 90 at% or less. The W source is not limited to the form described above as "containing W as the main component." For example, the W source may be composed of a composite material formed by combining W-based materials with other materials. For example, the W source may contain copper (Cu), silver (Ag), molybdenum (Mo), iron (Fe), cobalt (Co), nickel (Ni), gold (Au), thorium (Th), etc. Examples of this type of composite material include copper-tungsten composite materials and silver-tungsten composite materials. The W source may also be composed of a composite material formed by mixing W-based materials with ceramics. Examples of ceramics that may be included in the W source include high-melting-point ceramics such as tria (ThO2) and yttria (Y2O3).
[0033] (b) Cu source Similar to the W source described above, the Cu source can be any material containing the copper (Cu) element, and its form and specific components are not particularly limited. For example, the Cu source may be Cu powder substantially composed of Cu particles containing the Cu element. Using a fine Cu source such as Cu powder facilitates the diffusion of the Cu element during the reduction calcination treatment described later. From the viewpoint of more favorably facilitating the diffusion of the Cu element, the average particle size of the Cu powder is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less, and particularly preferably 2 μm or less. Furthermore, if the particle size of the Cu powder becomes too small, it tends to become difficult to handle the Cu source when preparing the oxidation contact. From this viewpoint, the average particle size of the Cu powder is preferably 10 nm or more, more preferably 20 nm or more, even more preferably 30 nm or more, and particularly preferably 50 nm or more. The Cu source may also be a Cu paste obtained by dispersing the above-mentioned Cu powder in a predetermined solvent. This facilitates contact between the W source and the Cu source, further improving the efficiency of W-Cu alloy production. In particular, when the W source is a solid metal component (W component), using Cu paste as the Cu source prevents the formation of voids between the W-Cu alloy and the W component after fabrication. When using Cu paste, the components other than Cu powder (solvent, binder, dispersant, etc.) are not particularly limited, and any components that can be added to a general metal paste can be used without any particular restrictions. Furthermore, the Cu source is not limited to the Cu powder described above, but may also be a solid metal component (Cu component) containing the element Cu. By using this Cu component as the Cu source, a metal laminate in which a W-Cu alloy layer is formed on the surface of the Cu component can be manufactured.
[0034] Furthermore, the Cu source used in this process can be any material containing the element Cu, and its composition is not particularly limited. Specifically, examples of metallic elements that can be mixed into the Cu source include gold (Au), nickel (Ni), aluminum (Al), tin (Sn), zinc (Zn), silica (Si), iron (Fe), manganese (Mn), cobalt (Co), and beryllium (Be). From the viewpoint of appropriately causing the diffusion of the element Cu during the reduction firing process, it is preferable that the Cu source contains the element Cu as its main component. Here, "containing the element Cu as its main component" means that elements other than the element Cu are not intentionally included. Therefore, if the Cu source contains unavoidable impurities (metallic elements other than the element Cu) derived from raw materials or manufacturing processes, these are included in the concept of "containing the element Cu as its main component" as defined herein. For example, if the total number of metallic elements constituting the Cu source is 100 at%, and the number of Cu atoms is 75 at% or more, it can be said that it "contains the element Cu as its main component." Furthermore, from the viewpoint of more appropriately facilitating the diffusion of Cu elements during the calcination process, the number of Cu atoms in the Cu source is preferably 77.5 at% or more, more preferably 80 at% or more, and particularly preferably 82.5 at% or more. The upper limit of the number of Cu atoms in the Cu source is not particularly limited and may be 99.5 at% or less, 97.5 at% or less, 95 at% or less, 92.5 at% or less, or 90 at% or less.
[0035] (c) Preparation of the oxidizing contact In the manufacturing method disclosed herein, an oxidation contact is prepared using the W source and Cu source described above. One example of a means for obtaining such an oxidation contact is to prepare a contact in which the W source and Cu source are in contact beforehand, and then perform an oxidation treatment on such a contact. The specific procedure for such a means will be described below.
[0036] (c-1) Preparation of the contacts As described above, a contact body is prepared in which a W source and a Cu source are in contact. The form of the contact body varies depending on the respective forms of the W source and Cu source, and is not limited to the technology disclosed herein. For example, if both the W source and the Cu source are solid metal members, the contact body can be prepared by bringing the respective metal members (W member and Cu member) into close contact. Also, if both the W source and the Cu source are powder materials, a mixed powder obtained by mixing the respective powder materials (W powder and Cu powder) can be prepared as the contact body. Furthermore, as described above, if a W member is prepared as the W source and Cu paste is prepared as the Cu source, the contact body can be prepared by applying the Cu paste to the surface of the W member. By bringing the W source and Cu source into contact by applying the paste in this way, the W source and Cu source can be easily brought into close contact, thus preventing the formation of voids between the W-Cu alloy and the W member after the reduction firing treatment. Furthermore, if a W component is prepared as the W source and Cu powder is prepared as the Cu source, the contact body can be prepared by bringing a molded body filled with Cu powder into contact with the W component.
[0037] (c-2) Oxidation treatment Next, the contact body described above is subjected to an oxidation treatment. This oxidizes both the W source and the Cu source, and an oxidized contact body is formed in which W oxide and Cu oxide are present at the boundary between the W source and the Cu source. The specific procedure for such an oxidation treatment is not particularly limited, and various conventionally known methods can be used without particular restriction. For example, in the oxidation treatment, the contact body may be heated in an oxidizing atmosphere. By performing such an oxidation treatment accompanied by heating, the W source and Cu source can be sufficiently oxidized in a short time, thus contributing to an improvement in the efficiency of oxidized contact body formation (i.e., the manufacturing efficiency of W-Cu alloy). It is preferable that, after this step, copper oxide is present in the Cu source in a region of at least 5 nm (more preferably 20 nm or more, even more preferably 50 nm or more, and particularly preferably 100 nm or more) from the surface in contact with the W source. By performing an oxidation treatment that sufficiently oxidizes the Cu source in this way, a W-Cu alloy with a thickness of 5 nm or more can be produced more appropriately. On the other hand, it is preferable that the W source after this process has tungsten oxide present in a region of at least 5 nm (more preferably 7 nm or more, even more preferably 10 nm or more, and particularly preferably 15 nm or more) from the surface in contact with the Cu source. By performing an oxidation treatment that sufficiently oxidizes the W source in this way, a W-Cu alloy with a thickness of 5 nm or more can be produced more appropriately.
[0038] When performing oxidation treatment accompanied by heating, it is preferable to set the heating temperature to 50°C or higher, more preferably 60°C or higher, even more preferably 80°C or higher, and particularly preferable to set it to 100°C or higher, in order to produce oxide of the predetermined thickness as described above. This appropriately promotes the oxidation of the W source and Cu source, and allows for the production of oxide of sufficient thickness. On the other hand, from the viewpoint of preventing the W source and Cu source from sintering during the oxidation treatment and preventing excessive oxidation of the Cu source, the upper limit of the heating temperature in the oxidation treatment is preferably 200°C or lower, more preferably 180°C or lower, even more preferably 160°C or lower, and particularly preferably 140°C or lower. By performing oxidation treatment under these conditions, monovalent copper oxide (copper(I) oxide) is formed on the surface of the Cu source after treatment. Furthermore, it is preferable to adjust the heating time in the oxidation treatment from the viewpoint of sufficiently oxidizing the W source and Cu source. As an example, the heating time in the oxidation treatment is preferably 0.5 hours or more, more preferably 1 hour or more, even more preferably 1.5 hours or more, and particularly preferably 2 hours or more. On the other hand, the upper limit of the heating time is not particularly limited and may be 24 hours or less, or 21 hours or less. Considering the improvement of manufacturing efficiency by shortening the oxidation treatment, the upper limit of the heating time in the oxidation treatment is preferably 10 hours or less, more preferably 7.5 hours or less, and particularly preferably 5 hours or less. However, these heating times in the oxidation treatment are not limited to the techniques disclosed herein and can be changed as appropriate. For example, by increasing the heating temperature, the heating time required to sufficiently oxidize the W source and Cu source can be shortened. In this specification, "heating temperature" refers to the maximum temperature in the heat treatment, and "heating time" refers to the time for which that maximum temperature is maintained. As mentioned above, the specific procedure for the oxidation treatment is not particularly limited as long as the W source and Cu source can be sufficiently oxidized. For example, if a contact body in which the W source and Cu source are in contact is left in an oxygen atmosphere for a long period of time (e.g., 10 days or more), an oxidized contact body in which the W source and Cu source are sufficiently oxidized can be obtained without performing a heat treatment.
[0039] (c-3) Other means Furthermore, the means for obtaining the oxidized contact is not limited to those described above, and various methods can be employed. For example, the surfaces of the W source and the Cu source may be oxidized individually, and then the oxidized surfaces may be brought into contact with each other. The W-Cu alloy disclosed herein can also be manufactured using an oxidized contact prepared by such means.
[0040] (2) Reduction firing treatment Next, in the manufacturing method disclosed herein, the oxidizing contact prepared as described above is subjected to a firing treatment under a reducing atmosphere. During this reducing firing treatment, mutual diffusion between W and Cu elements occurs, and a W-Cu alloy is formed. As described above, such a W-Cu alloy is an alloy material that was previously thought not to occur. Although not intended to limit the technology disclosed herein, the following hypothesis can be considered for the mechanism of formation of such an alloy material. In the manufacturing method disclosed herein, an oxidizing contact in which W oxide and Cu oxide are formed at the interface between the W source and the Cu source is used. When this oxidizing contact is subjected to a reducing firing treatment, a tungsten-copper composite oxide (W-Cu composite oxide) is formed in the initial stages of the firing treatment by mutual diffusion of W oxide and Cu oxide. If the reducing firing treatment is continued thereafter, the reduction of the W-Cu composite oxide progresses, and a W-Cu alloy is formed. Another example of a hypothesis for the mechanism of W-Cu alloy formation can also be considered as follows. When an oxidized copper source (copper oxide) is subjected to a reduction calcination treatment, the copper element is activated during the reduction reaction. This may have facilitated the diffusion of copper into the water source, resulting in the formation of a water-coated copper alloy.
[0041] In this reduction firing process, the heating temperature is preferably 750°C or higher, more preferably 800°C or higher, even more preferably 850°C or higher, and particularly preferably 900°C or higher. This improves the manufacturing efficiency of W-Cu alloy. On the other hand, if the heating temperature in the reduction firing process becomes too high, the W source and Cu source may melt, and W-Cu alloy may not be produced. From this viewpoint, the upper limit of the heating temperature is preferably 1250°C or lower, more preferably 1200°C or lower, even more preferably 1150°C or lower, and particularly preferably 1100°C or lower. In addition, the heating time in the reduction firing process is preferably 0.5 hours or more, and more preferably 1 hour or more. This allows for the proper production of W-Cu alloy. On the other hand, considering the improvement in manufacturing efficiency by shortening the reduction firing process, the upper limit of the heating time in this process is preferably 5 hours or less, more preferably 4 hours or less, and particularly preferably 3 hours or less.
[0042] Furthermore, the atmosphere during firing is not particularly limited as long as it is adjusted to a reducing atmosphere. Examples of reducing gases used to create a reducing atmosphere during firing include hydrogen (H2) gas and hydrocarbon gases (CH4, C3H8, etc.). Also, from the viewpoint of more appropriately producing W-Cu alloys, it is preferable to carry out the firing process in an atmosphere filled with a mixed gas of a neutral gas or inert gas and a reducing gas. By mixing in a neutral gas (or inert gas) in this way and lowering the concentration of the reducing gas, the temperature at which the reduction reaction of copper oxide, tungsten oxide, and copper-tungsten composite oxide is completed is raised. This suppresses the reduction of copper oxide, etc., back to copper in a low-temperature environment (around 200°C) and allows the oxidized state to be maintained until the temperature rises to a high-temperature environment. As a result, mutual diffusion between W element and Cu element is more likely to occur along with the reduction reaction, improving the efficiency of W-Cu alloy production. An example of an inert gas mixed with the reducing gas mentioned above is argon (Ar) gas. An example of a neutral gas is nitrogen (N2) gas or ammonia. Furthermore, the concentration of the reducing gas (e.g., hydrogen (H2) gas) in the mixed gas described above is preferably 20% or less, more preferably 1% to 5%, and can be set to, for example, 3%. By using a mixed gas with such a low concentration of reducing gas, the oxidation state can be maintained until the temperature rises to a high-temperature environment of 500°C or higher, and the reduction reaction can be generated in that high-temperature environment, thereby more favorably improving the production efficiency of W-Cu alloys.
[0043] 2.Alloy material Next, the alloy material produced by the manufacturing method disclosed herein will be described. According to the manufacturing method disclosed herein, an alloy material (W-Cu alloy material) is produced that mainly contains a W-Cu alloy in which Cu and W elements are mutually dispersed, and has a thickness of 5 nm or more. By using this W-Cu alloy material with a thickness of 5 nm or more, a W member and other metal members (for example, a Cu member) can be strongly joined. Specifically, even in the conventional technique of directly joining the Cu member and the W member as described above, diffusion of W and Cu elements may occur in a very narrow region of less than 1 nm (typically a few atoms) at the boundary between the Cu member and the W member. However, even if diffusion of W and Cu elements occurs in such a narrow region, the bonding strength between the W member and the Cu member is not dramatically improved. In contrast, according to the manufacturing method disclosed herein, a W-Cu alloy material with a thickness of 5 nm or more can be easily produced. In other words, according to the technique disclosed herein, an alloy material that can improve the bonding strength between a Cu member and a W member can be provided.
[0044] As stated above, the W-Cu alloy material disclosed herein contains W-Cu alloy as its main component. Here, "contains W-Cu alloy as its main component" means that elements other than W and Cu are intentionally omitted. Therefore, "W-Cu alloy material" in this specification includes metallic materials that contain trace amounts of unavoidable impurities derived from raw materials, manufacturing processes, etc., in addition to W and Cu. For example, the W-Cu alloy material disclosed herein includes metallic materials in which the total number of W and Cu atoms is 75 at% or more when the total number of constituent elements is set to 100 at%. Furthermore, from the viewpoint of ensuring better bonding with W members and Cu members, the total number of W and Cu atoms in the W-Cu alloy member is preferably 80 at% or more, more preferably 82.5 at% or more, and particularly preferably 85 at% or more. Furthermore, the upper limit of the total number of W and Cu atoms in the W-Cu alloy material is not particularly limited and may be 100 at% or less, 99.5 at% or less, 99 at% or less, 98 at% or less, or 97 at% or less. Elements that may be contained in the W-Cu alloy material (unavoidable impurities) include O, Cu, Pt, Mo, Fe, Pd, Ir, Au, Co, Ni, Zn, Al, Sn, Pb, Mn, Ag, and Th.
[0045] The ratio of W element to Cu element in a W-Cu alloy is not particularly limited. For example, when the total number of W and Cu elements in a W-Cu alloy is set to 100 at%, the number of W element atoms is preferably 5 at% to 50 at%. As the number of W element atoms increases, the bonding properties with W members tend to improve. From this viewpoint, the number of W element atoms is preferably 10 at% or more, more preferably 15 at% or more, and particularly preferably 20 at% or more. On the other hand, as the number of W element atoms decreases, the number of Cu element atoms increases relatively, and the bonding properties with Cu members tend to improve. From this viewpoint, the number of W element atoms is preferably 40 at% or less, more preferably 35% or less or more, and particularly preferably 30 at% or less.
[0046] Furthermore, as mentioned above, from the viewpoint of firmly joining the W member to other metal members, the W-Cu alloy material is required to have a thickness of 5 nm or more. In addition, from the viewpoint of further improving the bonding strength between the W member and other metal members, the thickness of the W-Cu alloy material is preferably 50 nm or more, preferably 100 nm or more, preferably 150 nm or more, and preferably 200 nm or more. The upper limit of the thickness of the W-Cu alloy member is not particularly limited and may be 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 500 nm or less.
[0047] 3. Metal Laminates and Metal Bonding The technology disclosed herein also allows for the fabrication of components (metal laminates and metal assemblies) containing W-Cu alloy. Each of these will be described in detail below.
[0048] (1) Metal laminate The technology disclosed herein provides a metal laminate in which a W-Cu alloy layer is formed on the surface of a W member. Such a metal laminate can be easily obtained, for example, by preparing a contact body in which Cu paste is applied to the surface of a W member, as described above. Alternatively, this metal laminate can be manufactured by welding a pre-formed W-Cu alloy material to the surface of a W member. This metal laminate can be easily joined to other metal members by using the W-Cu alloy layer as the joining surface. In other words, by using the metal laminate disclosed herein, a metal joint in which a W member and other metal members are joined can be easily manufactured. As described above, in order to ensure sufficient bonding strength between the W member and other metal members, the thickness of the W-Cu alloy layer in the metal laminate disclosed herein is set to 5 nm or more. The W member used in this metal laminate can be any solid metal member containing the element W, and its shape and composition are not particularly limited. For example, the W member of the metal laminate can be the same as the W member that can be used as a W source as described above, so redundant explanations are omitted.
[0049] (2) Metal bonded body A metal joint is formed by joining another metal member (to be joined) to the surface of the W-Cu alloy layer of a metal laminate comprising the W member and W-Cu alloy described above. This metal joint can be easily obtained, for example, by preparing a contact body in which Cu paste is placed between the W member and the to be joined during the preparation of the contact body described above. Alternatively, this metal joint can also be produced by welding the to be joined to the W-Cu alloy layer of the metal laminate described above.
[0050] In the technology disclosed herein, the object to be joined to the W member is not particularly limited, and conventionally known metal members can be used without any particular restriction. For example, the object to be joined may be a metal member different from the W member (a dissimilar metal member). Specifically, by joining the W member and the dissimilar metal member via the W-Cu alloy, the W member and the dissimilar metal member can be joined strongly and with high reliability. The dissimilar metal member is not particularly limited as long as it is a metal member that can be joined to the W-Cu alloy. Examples of such dissimilar metal members include metal members containing copper (Cu), nickel (Ni), zinc (Zn), and aluminum (Al). Among the dissimilar metal members mentioned above, Cu members containing copper as the main component are particularly suitable for joining to the W-Cu alloy and are relatively inexpensive metal members, making them suitable as an object to be joined. Specific examples of this Cu member include tough pitch copper, oxygen-free copper, copper alloys, and copper powder sintered bodies. Furthermore, the object to be joined to the W member in the technology disclosed herein is not limited to dissimilar metal members. In other words, the W-Cu alloy material disclosed herein can also be used when joining W members together.
[0051] As described above, the technology disclosed herein makes it possible to produce an alloy material (W-Cu alloy) containing W and Cu elements, which were previously thought not to interdiffuse. Furthermore, by using a W-Cu alloy material with a thickness of 5 nm or more, W members can be strongly bonded to other metal members. In other words, the technology disclosed herein enables strong and reliable bonding between tungsten members and other metal members, thereby contributing to improved performance of ultra-high temperature components such as divertors, accelerators, plasma discharge devices, high-temperature furnaces, and thin-film deposition devices. It should be noted that the applications of the W-Cu alloy disclosed herein are not limited to bonding W members, but can also be used as a barrier film to protect the surface of metal members (e.g., W members), a catalyst, etc.
[0052] [Example Test] The following describes test examples relating to the present invention, but these test examples are not intended to limit the present invention.
[0053] In this study, three types of metal joints (Samples 1-3) were fabricated by joining W members and Cu members, and various analyses were performed on each of these metal joints.
[0054] (1) Sample 1 First, Cu paste was applied to the entire surface of one side of a Cu component (a tough pitch copper plate measuring 0.3 mm thick x 15 mm x 15 mm). Then, a W component (a tungsten plate measuring 0.3 mm thick x 7.5 mm x 7.5 mm) was placed on top of the Cu paste and lightly pressed down with a finger to create a contact surface where the W component and the Cu paste were in contact. The Cu paste used in this sample contained 90 wt% Cu powder with an average particle size of 1 μm. The materials other than Cu powder were glass powder, a binder (ethyl cellulose resin), a dispersant, and a solvent.
[0055] Next, an oxidized contact was prepared by performing a heat treatment on the aforementioned contact by heating it at 120°C for 4 hours under an oxidizing atmosphere. When the Cu paste dried, the resulting Cu film was observed to be slightly reddish. From this, it is understood that the Cu powder was oxidized by the heat treatment described above, producing red copper(I) oxide. The oxidized contact was then moved to a reducing atmosphere filled with N2-H2 (3%) gas, and a binder removal treatment (heating rate: 10°C / min, heating temperature: 400°C, heating time: 1 hour) was performed. Then, while maintaining the reducing atmosphere, a calcination treatment (heating rate: 5°C / min, maximum temperature: 1000°C, calcination time: 30 minutes) was performed. The calcined sample was then cooled to room temperature to obtain sample 1. Sample 1 was then polished by ion milling, and SEM observation and EDX analysis were performed. The results are shown in Figure 1. In Figure 1, (a) is a cross-sectional SEM image (100,000x magnification), (b) is the elemental map of Cu, and (c) is the elemental map of W.
[0056] As shown in Figure 1, in Sample 1, it was confirmed that a W-Cu alloy was formed between the W member and the Cu member, with W and Cu elements mutually diffused. This indicates that by performing a reduction firing treatment on an oxidizing contact body where W oxide and Cu oxide exist at the boundary between the W source and the Cu source, mutual diffusion of W and Cu elements, which was previously thought not to occur, can be achieved. Furthermore, the thickness of the W-Cu alloy observed in Sample 1 was approximately 230 nm. The metal joint between the W member and the Cu member joined via a W-Cu alloy of this thickness exhibited extremely high strength.
[0057] (2) Sample 2 Here, Sample 2 was prepared under the same conditions as Sample 1, except that the heat treatment time before the reduction firing process was extended to 21 hours. Observation of the surface coated with Cu paste after the heat treatment revealed that a Cu film with a stronger reddish tint than that of Sample 1 had formed. This suggests that the Cu powder in this sample was also oxidized by the heat treatment. SEM observation and EDX analysis were then performed on Sample 2 under the same conditions as Sample 1. The results are shown in Figure 2. In Figure 2, (a) is a cross-sectional SEM image (100,000x magnification), (b) is the elemental map of Cu, and (c) is the elemental map of W. Furthermore, EDX analysis was performed on points 1 to 3 in the 100,000x cross-sectional SEM images of Sample 2, and the ratio of W to Cu atoms (at%) was measured. The measurement results are shown in Table 1 below.
[0058] [Table 1]
[0059] As shown in Figures 2-3 and Table 1, in Sample 2 as well, a W-Cu alloy was formed in which W and Cu elements diffused with each other between the W member and the Cu member (for example, point 2 in Figure 3). From this, it was found that a W-Cu alloy can be formed even when the oxidation treatment time is extended to 21 hours. Furthermore, in Sample 2, as in Sample 1, the thickness of the W-Cu alloy exceeded 5 nm, indicating very strong bonding strength.
[0060] (3) Sample 3 Here, Sample 3 was prepared under the same conditions as Sample 1, except that the heat treatment time before the reduction firing process was shortened to 30 minutes. When the surface coated with Cu paste after the heat treatment was observed, the red film seen in Samples 1 and 2 was not formed. From this, it can be concluded that the oxidation of the Cu powder was insufficient in this sample. Next, SEM observation and EDX analysis were performed on the prepared Sample 3 under the same conditions as Sample 1. The results are shown in Figure 4. In Figure 4, (a) is a cross-sectional SEM image (50,000x magnification), (b) is the elemental map of O, (c) is the elemental map of Cu, and (d) is the elemental map of W.
[0061] As shown in Figure 3, in Sample 3, the boundary between the Cu and W members is clearly visible, indicating that no interdiffusion between W and Cu elements occurred. This suggests that if the Cu and W members are not sufficiently oxidized before the reduction firing treatment, a W-Cu alloy will not be formed. From these experimental results, it was found that in order to produce a W-Cu alloy in which W and Cu elements are mutually diffused, it is necessary to perform an oxidation treatment in which the Cu and W sources are oxidized, followed by a firing treatment in a reducing atmosphere.
[0062] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above.
Claims
1. A method for producing a metal joint in which a W member containing tungsten (W) and a Cu member containing copper (Cu) are joined via a W-Cu alloy of 5 nm or more, The W member and the Cu member are arranged such that an oxidized contact body, in which W and Cu are oxidized, is interposed at the boundary between the W member and the Cu member, and the oxidized contact body is subjected to a firing treatment in a reducing atmosphere. A method for manufacturing a metal joint, wherein, before performing the firing treatment, at least 5 nm or more of copper oxide is present between the W member and the Cu member.
2. The method for manufacturing a metal joint according to claim 1, wherein the oxidized contact body is prepared by performing an oxidation treatment on the contact body in which the W member and the Cu member are in contact.
3. A method for producing a metal joint in which a W member containing tungsten (W) and a Cu member containing copper (Cu) are joined via a W-Cu alloy of 5 nm or more, The W member and the Cu member are arranged such that an oxidized contact body, in which W and Cu are oxidized, is interposed at the boundary between the W member and the Cu member, and the oxidized contact body is subjected to a firing treatment in a reducing atmosphere. A method for manufacturing a metal joint, wherein, before performing the firing treatment, at least tungsten oxide with a thickness of 5 nm or more is present between the W member and the Cu member.
4. A method for producing a metal laminate in which a W-Cu alloy with a wavelength of 5 nm or more is laminated on the surface of a W member containing the element tungsten (W), A Cu paste containing copper (Cu) is applied to the surface of the W member. An oxidized contact body is formed on the surface of the W member in which W and Cu are oxidized. The aforementioned oxidation contact is subjected to calcination treatment under a reducing atmosphere. A method for manufacturing a metal laminate, wherein, before performing the firing treatment, copper oxide is present in a region of at least 5 nm from the surface of the W member.
5. A method for producing a metal laminate in which a W-Cu alloy with a wavelength of 5 nm or more is laminated on the surface of a W member containing the element tungsten (W), A Cu paste containing copper (Cu) is applied to the surface of the W member. An oxidized contact body is formed on the surface of the W member in which W and Cu are oxidized. The aforementioned oxidation contact is subjected to calcination treatment under a reducing atmosphere. A method for manufacturing a metal laminate, wherein, before performing the firing treatment, tungsten oxide is present in a region of at least 5 nm from the surface of the W member.