Composite material

Abstract

This composite material comprises a tungsten layer, an iron-based metal layer, and a bonding layer. The bonding layer contains titanium and is positioned between the tungsten layer and the iron-based metal layer. The bonding layer includes a carbide-containing embrittlement layer. The embrittlement layer is positioned at the interface between the iron-based metal layer and the bonding layer. The thickness of the embrittlement layer is 3.3 µm or less.

Description

Composite material

[0001] The present disclosure relates to a composite material. The present application claims priority based on Japanese Patent Application No. 2025-051962, a Japanese patent application filed on March 26, 2025. All the contents described in the said Japanese patent application are incorporated herein by reference.

[0002] Japanese Unexamined Patent Application Publication No. 2004-209530 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2022-069712 (Patent Document 2) disclose a method for joining an iron-based metal and tungsten.

[0003] Japanese Unexamined Patent Application Publication No. 2004-209530 Japanese Unexamined Patent Application Publication No. 2022-069712

[0004] The composite material according to the present disclosure includes a tungsten layer, an iron-based metal layer, and a bonding layer. The bonding layer contains titanium and is located between the tungsten layer and the iron-based metal layer. The bonding layer includes an embrittled layer containing carbide. The embrittled layer is located at the interface between the iron-based metal layer and the bonding layer. The thickness of the embrittled layer is 3.3 μm or less.

[0005] FIG. 1 is a schematic cross-sectional view showing the configuration of the composite material according to the first embodiment. FIG. 2 is an enlarged view of a region II in FIG. 1. FIG. 3 is a schematic cross-sectional view showing a step of forming a titanium layer on one end surface of the tungsten layer. FIG. 4 is a schematic cross-sectional view showing a step of forming a titanium layer on one end surface of the iron-based metal layer. FIG. 5 is a schematic cross-sectional view showing the configuration of the composite material according to the second embodiment. FIG. 6 is an evaluation result of Group 1. FIG. 7 is an evaluation result of Group 2. FIG. 8 is an evaluation result of Group 3.

[0006] [Problem to be Solved by the Present Disclosure] An object of the present disclosure is to provide a composite material having high bonding strength.

[0007] [Effect of the Present Disclosure] According to the present disclosure, a composite material having high bonding strength can be provided.

[0008] [Summary of Embodiments of the Present Disclosure] First, an outline of embodiments of the present disclosure will be described.

[0009] (1) The composite material relating to this disclosure comprises a tungsten layer, an iron-based metal layer, and a bonding layer. The bonding layer contains titanium and is located between the tungsten layer and the iron-based metal layer. The bonding layer includes an embrittlement layer containing carbides. The embrittlement layer is located at the interface between the iron-based metal layer and the bonding layer. The thickness of the embrittlement layer is 3.3 μm or less.

[0010] (2) The composite material relating to (1) above may be in the form of a plate. (3) The composite material relating to (1) above may be in the form of an arc in a cross section parallel to the lamination direction.

[0011] (4) In the composite material relating to any of (1) to (3) above, the thickness of the bonding layer may be 10 μm or more.

[0012] (5) In the composite material relating to any of (1) to (4) above, the Vickers hardness of the tungsten layer may be 400 HV or more.

[0013] [Details of Embodiments of the Disclosure] The details of embodiments of the disclosure are described below. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description of them is not repeated.

[0014] (First Embodiment) Figure 1 is a schematic cross-sectional view showing the configuration of a composite material according to the first embodiment. As shown in Figure 1, the composite material 1 according to the first embodiment has a tungsten layer 10, a bonding layer 20, and an iron-based metal layer 30. The bonding layer 20 is located on the tungsten layer 10. The iron-based metal layer 30 is located on the bonding layer 20. The bonding layer 20 is located between the tungsten layer 10 and the iron-based metal layer 30. The bonding layer 20 is connected to each of the tungsten layer 10 and the iron-based metal layer 30. The bonding layer 20 contains titanium (Ti).

[0015] The tungsten layer 10 is formed of, for example, pure tungsten. In the tungsten layer 10, the tungsten (W) content may be, for example, 99% by mass or more. The tungsten layer 10 may contain potassium (K) as an additive to increase the recrystallization temperature. The tungsten layer 10 is, for example, plate-shaped tungsten. The relative density of the tungsten layer 10 may be 99% or more, or substantially 100%.

[0016] The iron-based metal layer 30 is an alloy containing iron as the primary component (the component with the highest content). The iron-based metal layer 30 belongs to the group of, for example, pure iron, ordinary steel, special steel, cast iron, and cast steel. Examples of the iron-based metal layer 30 include F82H (Fe-8 mass%Cr-2 mass%W-0.2 mass%V-0.04 mass%Ta), SUS430 (Fe-18 mass%Cr), or EUROFER97 (Fe-9 mass%Cr-1 mass%W-0.2 mass%V-0.14 mass%Ta).

[0017] The iron-based metal layer 30 may be an alloy containing chromium as the second component (the component with the second highest content). In the iron-based metal layer 30, the chromium content may be, for example, 3% by mass or more and 25% by mass or less, 5% by mass or more and 22% by mass or less, or 7% by mass or more and 20% by mass or less.

[0018] The composite material 1 according to the first embodiment is plate-shaped. The composite material 1 may be, for example, a disc shape or a rectangular plate shape. As shown in Figure 1, the thickness of the tungsten layer 10 is a first thickness T1. The first thickness T1 is, for example, 1 mm. The first thickness T1 may be 0.5 mm or more and 3 mm or less. When the tungsten layer 10 is disc-shaped, the diameter of the tungsten layer 10 is, for example, 30 mm.

[0019] The thickness of the iron-based metal layer 30 is defined as a third thickness T3. The third thickness T3 is, for example, 1 mm. The third thickness T3 may be between 0.5 mm and 3 mm. If the iron-based metal layer 30 is disc-shaped, the diameter of the iron-based metal layer 30 is, for example, 30 mm.

[0020] The thickness of the bonding layer 20 is defined as the second thickness T2. The second thickness T2 is, for example, 10 μm. The second thickness T2 may be smaller than the first thickness T1. The second thickness T2 may be smaller than the third thickness T3. The second thickness T2 may be 10 μm or more, 20 μm or more, or 50 μm or more. The second thickness T2 may be 1000 μm or less, or 500 μm or less.

[0021] The Vickers hardness of the tungsten layer 10 is, for example, 400 HV or higher. The Vickers hardness of the tungsten layer 10 may be 450 HV or higher, 500 HV or higher, or 550 HV or higher. The Vickers hardness of the tungsten layer 10 may be 600 HV or lower, or 580 HV or lower.

[0022] Figure 2 is an enlarged view of region II in Figure 1. As shown in Figure 2, the bonding layer 20 includes an embrittlement layer 40. Specifically, the bonding layer 20 is formed by the embrittlement layer 40 and the titanium layer 50. The embrittlement layer 40 is located at the interface between the iron-based metal layer 30 and the bonding layer 20. The embrittlement layer 40 is continuous with the iron-based metal layer 30. The embrittlement layer 40 is located between the titanium layer 50 and the iron-based metal layer 30.

[0023] The embrittlement layer 40 contains carbides. Specifically, the embrittlement layer 40 contains titanium carbide (TiC). The embrittlement layer 40 may also contain a compound of titanium and iron (Fe). Specifically, the embrittlement layer 40 may contain TiFe or TiFe2. The embrittlement layer 40 may contain TiC and TiFe, or TiC and TiFe2, or TiC, TiFe and TiFe2. The crystalline phase of the compound contained in the embrittlement layer 40 can be identified using an X-ray diffractometer.

[0024] As shown in Figure 2, the thickness of the embrittlement layer 40 is defined as the fourth thickness T4. The fourth thickness T4 is 3.3 μm or less. The fourth thickness T4 may be 3 μm or less, 2.5 μm or less, 2 μm or less, 1.5 μm or less, 1 μm or less, or 0.5 μm or less. The fourth thickness T4 may be 0.01 μm or more. The thickness of the embrittlement layer 40 can be measured using a scanning electron microscope (SEM).

[0025] The bonding strength of composite material 1 is, for example, 275 MPa or more. The bonding strength of composite material 1 is determined as the tensile stress of composite material 1 in the lamination direction. The bonding strength of composite material 1 may be 280 MPa or more, 284 MPa or more, or 288 MPa or more. The bonding strength of composite material 1 may be 294 MPa or less, or 292 MPa or less.

[0026] In the lamination direction, the thermal conductivity of composite material 1 is, for example, 40 W / mK or higher. In the lamination direction, the thermal conductivity of composite material 1 may be 41 W / mK or higher and 53 W / mK or lower, or 43 W / mK or higher and 51 W / mK or lower.

[0027] Next, an example of the application of the composite material 1 according to this embodiment will be described. The composite material 1 according to this embodiment can be used, for example, as a blanket material for a nuclear fusion reactor. A nuclear fusion reactor has a structure in which a blanket is arranged to surround the core plasma. The structural material of the blanket is formed from, for example, low-activation ferritic steel such as F82H. Since the surface of the blanket is exposed to high-temperature plasma, it is necessary to protect the low-activation ferritic steel with an armor material such as tungsten.

[0028] In this embodiment, the composite material 1 has a tungsten layer 10 bonded to an iron-based metal layer 30 via a bonding layer 20. Therefore, it is suitable for use as a blanket material for a nuclear fusion reactor. However, the composite material 1 in this embodiment is not limited to a blanket for a nuclear fusion reactor and may be used for applications other than a blanket for a nuclear fusion reactor.

[0029] <Method for Manufacturing Composite Materials> Next, a method for manufacturing the composite material 1 according to the first embodiment will be described. First, a disc-shaped tungsten layer 10 and a disc-shaped iron-based metal layer 30 are prepared. The thickness of the tungsten layer 10 is, for example, 1.0 mm. The diameter of the tungsten layer 10 is, for example, 30 mm. The thickness of the iron-based metal layer 30 is, for example, 1.0 mm. The diameter of the iron-based metal layer 30 is, for example, 30 mm.

[0030] Next, pretreatment is performed on each of the tungsten layer 10 and the iron-based metal layer 30. Specifically, a titanium layer (first titanium layer 21) is formed on one end face of the tungsten layer 10. Figure 3 is a schematic cross-sectional view showing the process of forming a titanium layer on one end face of the tungsten layer. As shown in Figure 3, the thickness of the first titanium layer 21 is set to a fifth thickness T5. The fifth thickness T5 is, for example, 5 μm. The first titanium layer 21 is formed, for example, by sputtering. The first titanium layer 21 may also be formed by plating or vapor deposition. The first titanium layer 21 may also be a foil.

[0031] Similarly, a titanium layer (second titanium layer 22) is formed on one end face of the iron-based metal layer 30. Figure 4 is a schematic cross-sectional view showing the process of forming a titanium layer on one end face of the iron-based metal layer. As shown in Figure 4, the thickness of the second titanium layer 22 is set to a sixth thickness T6. The sixth thickness T6 is, for example, 5 μm. The second titanium layer 22 is formed, for example, by sputtering. The second titanium layer 22 may also be formed by plating or vapor deposition. The second titanium layer 22 may also be a foil.

[0032] Next, the tungsten layer 10 on which the first titanium layer 21 is formed is subjected to heat treatment. Specifically, the tungsten layer 10 on which the first titanium layer 21 is formed is heat-treated in a vacuum. The heat treatment temperature is, for example, 890°C to 1000°C. The heat treatment time is 10 minutes to 60 minutes. This increases the bonding strength between the first titanium layer 21 and the tungsten layer 10. Titanium transforms into the same bcc structure as tungsten at temperatures of 885°C or higher. When the crystal structures are the same, mutual diffusion between titanium and tungsten is more likely to occur. By setting the heat treatment temperature to 890°C or higher, mutual diffusion between titanium and tungsten is promoted, thereby ensuring sufficient bonding strength.

[0033] Similarly, the iron-based metal layer 30 on which the second titanium layer 22 is formed is subjected to heat treatment. Specifically, the iron-based metal layer 30 on which the second titanium layer 22 is formed is heat-treated in a vacuum. The heat treatment temperature is, for example, 890°C to 1000°C. The heat treatment time is 10 minutes to 60 minutes. This increases the bonding strength between the second titanium layer 22 and the iron-based metal layer 30. By setting the heat treatment temperature to 1000°C or lower, it is possible to prevent the formation of brittle intermetallic compounds on the surface of the iron-based metal layer 30.

[0034] By performing heat treatment on the iron-based metal layer 30 on which the second titanium layer 22 is formed, the carbon and titanium contained in the iron-based metal layer 30 react. As a result, an embrittlement layer 40 containing TiC is formed at the interface between the second titanium layer 22 and the iron-based metal layer 30. However, an embrittlement layer 40 containing TiC is not formed at the interface between the first titanium layer 21 and the tungsten layer 10.

[0035] Next, the first titanium layer 21 formed on the tungsten layer 10 and the second titanium layer 22 formed on the iron-based metal layer 30 are arranged to be in contact with each other while facing each other. In this state, a diffusion bonding process is carried out. The first titanium layer 21 and the second titanium layer 22 are diffusion-bonded to form a bonded layer 20. The diffusion bonding method is, for example, the Spark Plasma Sintering (SPS) method. The temperature of the diffusion bonding process is, for example, 600°C or higher. The pressure of the diffusion bonding process is 50 MPa or higher. If the temperature of the diffusion bonding process exceeds 1000°C, the tungsten layer 10 becomes embrittle due to recrystallization. Also, if the temperature of the diffusion bonding process is 900°C or higher, the embrittlement layer 40 containing TiC tends to become thicker.

[0036] The temperature of the diffusion bonding process should preferably be 850°C or lower. This prevents the embrittlement layer 40 containing TiC from becoming excessively thick. Lowering the temperature of the diffusion bonding process makes it easier for unbonded areas to occur, but increasing the pressure prevents the occurrence of unbonded areas. In addition, the hot press method may be used instead of the SPS method.

[0037] (Second Embodiment) Next, the configuration of the composite material 1 according to the second embodiment will be described. The composite material 1 according to the second embodiment differs from the composite material 1 according to the first embodiment in that its cross-section parallel to the lamination direction is arc-shaped, but the other configurations are substantially the same as those of the composite material 1 according to the first embodiment. The following description will focus on the configurations that differ from the composite material 1 according to the first embodiment.

[0038] Figure 5 is a schematic cross-sectional view showing the structure of the composite material 1 according to the second embodiment. As shown in Figure 5, the composite material 1 according to the second embodiment has an arc shape in a cross-section parallel to the lamination direction. The lamination direction is the direction in which the tungsten layer 10, the bonding layer 20, and the iron-based metal layer 30 are laminated.

[0039] As shown in Figure 5, in a cross-section parallel to the lamination direction, the composite material 1 is curved so as to be convex in the direction from the iron-based metal layer 30 toward the tungsten layer 10. In a cross-section parallel to the lamination direction, the tungsten layer 10, the bonding layer 20, and the iron-based metal layer 30 are each arc-shaped. The composite material may also be hemispherical in shape.

[0040] In a cross-section parallel to the lamination direction, the central angle θ of the composite material is, for example, 90° or more and 180° or less. The central angle θ of the composite material may also be, for example, 120° or more, or 150° or more. The central angle θ of the composite material is determined as the central angle of the arc along the surface of the iron-based metal layer 30.

[0041] In a cross-section parallel to the lamination direction, the radius of curvature R of the composite material is, for example, 10 mm or more and 100 mm or less. The radius of curvature R of the composite material is determined as the radius of curvature of the arc along the surface of the iron-based metal layer 30.

[0042] Next, the effects of the composite material 1 according to this embodiment will be described. The composite material 1 according to this embodiment has a tungsten layer 10, an iron-based metal layer 30, and a bonding layer 20. The bonding layer 20 contains titanium and is located between the tungsten layer 10 and the iron-based metal layer 30. The bonding layer 20 includes an embrittlement layer 40 containing carbides. The embrittlement layer 40 is located at the interface between the iron-based metal layer 30 and the bonding layer 20. The thickness of the embrittlement layer 40 is 3.3 μm or less. This makes it possible to increase the bonding strength of the composite material 1.

[0043] According to the composite material 1 of this embodiment, the thickness of the bonding layer 20 may be 10 μm or more. If the thickness of the bonding layer 20 is excessively thin, it will not be possible to secure sufficient distance for tungsten and titanium to diffuse, and the bonding strength will decrease. By making the thickness of the bonding layer 20 containing titanium 10 μm or more, the bonding strength of the composite material 1 can be increased.

[0044] According to the composite material 1 of this embodiment, the Vickers hardness of the tungsten layer 10 may be 400 HV or higher. This prevents the composite material 1 from being damaged when it is attached to other components.

[0045] (1) Sample preparation Composite materials 1 according to Samples 1 to 32 were prepared. The composite materials 1 according to Samples 1 to 16 belong to Group 1. The composite materials 1 according to Samples 17 to 24 belong to Group 2. The composite materials 1 according to Samples 25 to 32 belong to Group 3. The methods for producing the composite materials 1 according to Samples 1 to 4, 17, 18, 25, and 26 are comparative examples. The methods for producing the composite materials 1 according to Samples 5 to 16, 19 to 24, and 27 to 32 are working examples. In Groups 1, 2, and 3, the Vickers hardness of the tungsten layer 10 before bonding was 565 HV, 463 HV, and 401 HV, respectively.

[0046] (1-1) Production method of comparative example First, a disc-shaped tungsten layer 10, a disc-shaped iron-based metal layer 30, and a disc-shaped titanium layer 50 were prepared by using electric discharge wire cutting. The thickness of the tungsten layer 10 is 1.0 mm. The diameter of the tungsten layer 10 is 30 mm. The thickness of the iron-based metal layer 30 is 1.0 mm. The diameter of the iron-based metal layer 30 is 30 mm. The thickness of the titanium layer 50 is 1.0 mm. The diameter of the titanium layer 50 is 30 mm. In Samples 1 and 3, the iron-based metal layer 30 was SUS430. In Samples 2, 4, 17, 18, 25, and 26, the iron-based metal layer 30 was F82H.

[0047] Next, each surface of the tungsten layer 10 and the iron-based metal layer 30 was ground by a surface grinder. The grit size of the grinder was #80.

[0048] Next, the tungsten layer 10, the titanium layer 50, and the iron-based metal layer 30 were laminated in this order. In this state, a diffusion bonding step was performed. The diffusion bonding method adopted was the SPS method. The temperature of the diffusion bonding step was 900°C or higher and 1250°C or lower. The pressure of the diffusion bonding step was 50 MPa. The duration of the diffusion bonding step was 30 minutes or more and 60 minutes or less.

[0049] (1-2) Manufacturing method of the example First, a disc-shaped tungsten layer 10 and a disc-shaped iron-based metal layer 30 were prepared using electrical discharge wire processing. The thickness of the tungsten layer 10 is 1.0 mm. The diameter of the tungsten layer 10 is 30 mm. The thickness of the iron-based metal layer 30 is 1.0 mm. The diameter of the iron-based metal layer 30 is 30 mm. In samples 5, 7, 9, 11, 13, and 15, the iron-based metal layer 30 was made of SUS430. In samples 6, 8, 10, 12, 14, 16, 19 to 24, and 27 to 32, the iron-based metal layer 30 was made of F82H.

[0050] Next, the surfaces of the tungsten layer 10 and the iron-based metal layer 30 were ground using a surface grinding machine. The grinding machine was set to #80 grit.

[0051] Next, pretreatment was performed on both the tungsten layer 10 and the iron-based metal layer 30. Specifically, a titanium layer 50 was formed by sputtering on one end face of each of the tungsten layer 10 and the iron-based metal layer 30. The thickness of the titanium layer 50 was set to 10 μm.

[0052] Next, the tungsten layer 10 on which the titanium layer 50 was formed was subjected to heat treatment. Specifically, the tungsten layer 10 on which the titanium layer 50 (first titanium layer 21) was formed was heat-treated in a vacuum. The heat treatment temperature was set to 900°C. The heat treatment time was set to 30 minutes.

[0053] Similarly, heat treatment was performed on the iron-based metal layer 30 on which the titanium layer 50 was formed. Specifically, the iron-based metal layer 30 on which the titanium layer 50 (second titanium layer 22) was formed was heat-treated in a vacuum. The heat treatment temperature was 900°C. The heat treatment time was 30 minutes.

[0054] Next, the titanium layer 50 formed on the tungsten layer 10 and the titanium layer 50 formed on the iron-based metal layer 30 are arranged to be in contact with each other. In this state, a diffusion bonding process is carried out. The first titanium layer 21, which is the titanium layer 50 formed on the tungsten layer 10, and the second titanium layer 22, which is the titanium layer 50 formed on the iron-based metal layer 30, are diffusion-bonded to form a bonded layer 20. The diffusion bonding method used was the SPS method. The temperature of the diffusion bonding process was set to 600°C or higher and 850°C or lower. The pressure of the diffusion bonding process was set to 50 MPa. The duration of the diffusion bonding process was set to 15 minutes or higher and 60 minutes or lower. As a result, a composite material 1 composed of the tungsten layer 10, the bonded layer 20, and the iron-based metal layer 30 was manufactured.

[0055] (2) Evaluation Method (2-1) Measurement of the thickness of the embrittlement layer 40 containing TiC A sample was cut from composite material 1, and the cross-section was roughly polished with waterproof sandpaper and buffed with a diamond suspension to make a mirror surface. The thickness of the embrittlement layer 40 containing TiC was measured by backscattered electron images taken with a SEM (JSM-7600F) manufactured by JEOL Ltd. The magnification of the SEM was set to 3000x. If the thickness of the embrittlement layer 40 appeared to be 0.1 μm or less in the SEM image, the magnification of the SEM was set to 10000x. The composition of the embrittlement layer 40 was measured using a Cu-Kα source with an X-ray diffractometer (SmartLab) manufactured by Rigaku.

[0056] (2-2) Joint Strength Measurement The joint strength of composite material 1 was determined by measuring the tensile strength using a precision universal testing machine (Autograph AG-XPlus) manufactured by Shimadzu Corporation. First, the iron-based metal layer 30 and the tungsten layer 10 were joined via a bonding layer 20 to create a joint body with a length of 30 mm. Then, a plate-shaped tensile test specimen with a width of 3 mm near the center in the longitudinal direction, a length of 8 mm in the longitudinal direction, and a thickness of 2 mm was cut from the joint body. The iron-based metal layer 30 and the tungsten layer 10 were pulled apart along the lamination direction, and the tensile strength at which the iron-based metal layer 30 and the tungsten layer 10 fractured was defined as the joint strength. The temperature of the tensile test was room temperature (27°C). The crosshead speed was set to 0.32 mm / min. The strain rate was set to 0.04 mm / min.

[0057] (2-3) Thermal Conductivity Measurement The thermal conductivity of composite material 1 was measured by the laser flash method. Thermal conductivity was calculated using the formula: thermal conductivity = thermal diffusivity × density × specific heat. Thermal diffusivity was measured at room temperature using an LFA447 Nanoflash manufactured by NETZSCH. The sample used for measuring thermal diffusivity was cut from composite material 1. The shape of the sample was a 10 mm diameter disc. The density of the materials constituting composite material 1 was measured by the Archimedes method. The specific heat of the materials constituting composite material 1 was calculated by multiplying the specific heat of various materials, based on the "Metal Data Book 4th Edition" edited by the Japan Institute of Metals (2004, Maruzen Publishing), by the weight ratio of various materials obtained by inductively coupled plasma emission spectroscopy.

[0058] (2-4) Measurement of Tungsten Hardness The Vickers hardness of the tungsten layer 10 was measured using a micro-Vickers hardness tester MMT-X manufactured by Matsuzawa Co., Ltd. The Vickers hardness was determined from the size of the indentation made when an indenter was pressed into the cross-section of the tungsten layer 10 with a constant load. The number of measurement points for Vickers hardness was set to five or more. The Vickers hardness of the tungsten layer 10 was set to the average value of the measured Vickers hardness. The test load was set to 100 gf. 1 gf (gram-weight) is approximately 9.8 mN (millineuton). The test temperature was set to room temperature. Room temperature means between 5°C and 35°C. First, the Vickers hardness of the tungsten before bonding was measured. Next, the Vickers hardness of the tungsten after bonding was measured. The Vickers hardness of the tungsten after bonding, divided by the Vickers hardness of the tungsten before bonding, was defined as the rate of change in tungsten hardness.

[0059] (3) Evaluation Results Figures 6, 7, and 8 show the thickness of the embrittlement layer containing TiC in composite material 1, the bonding strength of composite material 1, the thermal conductivity of composite material 1, the Vickers hardness of tungsten after bonding, and the rate of change of Vickers hardness of tungsten. Figures 6, 7, and 8 show the evaluation results for group 1, group 2, and group 3, respectively.

[0060] (3-1) Thickness of the embrittlement layer 40 containing TiC As shown in Figure 6, the thickness of the embrittlement layer 40 containing TiC in the composite material 1 for samples 1 to 4 was 3.5 μm or more and 5 μm or less. On the other hand, the thickness of the embrittlement layer 40 containing TiC in the composite material 1 for samples 5 to 16 was 3.3 μm or less.

[0061] As shown in Figure 7, the thickness of the embrittlement layer 40 containing TiC in the composite material 1 for samples 17 and 18 was between 3.4 μm and 5.1 μm. On the other hand, the thickness of the embrittlement layer 40 containing TiC in the composite material 1 for samples 19 to 24 was 3.3 μm or less.

[0062] As shown in Figure 8, the thickness of the embrittlement layer 40 containing TiC in the composite material 1 for samples 25 and 26 was between 3.6 μm and 5.4 μm. On the other hand, the thickness of the embrittlement layer 40 containing TiC in the composite material 1 for samples 27 to 32 was 3.2 μm or less.

[0063] (3-2) Bonding Strength Measurement As shown in Figure 6, the bonding strength of the composite material 1 for samples 1 to 4 was between 225 MPa and 240 MPa. In the composite material 1 for samples 1 to 4, the composite material fractured at the interface between the titanium layer 50 and the iron-based metal layer 30. On the other hand, the bonding strength of the composite material 1 for samples 5 to 16 was between 280 MPa and 295 MPa. In the composite material 1 for samples 5 to 16, the composite material fractured at the interface between the titanium layer 50 and the tungsten layer 10.

[0064] As shown in Figure 7, the bonding strength of the composite material 1 for samples 17 and 18 was between 223 MPa and 246 MPa. In the composite material 1 for samples 17 and 18, the composite material fractured at the interface between the titanium layer 50 and the iron-based metal layer 30. On the other hand, the bonding strength of the composite material 1 for samples 19 to 24 was between 277 MPa and 293 MPa. In the composite material 1 for samples 19 to 24, the composite material fractured at the interface between the titanium layer 50 and the tungsten layer 10.

[0065] As shown in Figure 8, the bonding strength of the composite material 1 for samples 25 and 26 was between 219 MPa and 239 MPa. In the composite material 1 for samples 25 and 26, the composite material fractured at the interface between the titanium layer 50 and the iron-based metal layer 30. On the other hand, the bonding strength of the composite material 1 for samples 27 to 32 was between 278 MPa and 294 MPa. In the composite material 1 for samples 27 to 32, the composite material fractured at the interface between the titanium layer 50 and the tungsten layer 10.

[0066] (3-3) Thermal Conductivity No significant differences were observed between the comparative examples and the examples in terms of thermal conductivity. As shown in Figure 6, the thermal conductivity of composite material 1 for samples 1 to 4 was 41 W / mK or more and 49 W / mK or less. On the other hand, the thermal conductivity of composite material 1 for samples 5 to 16 was 42 W / mK or more and 51 W / mK or less. As shown in Figure 7, the thermal conductivity of composite material 1 for samples 17 and 18 was 44 W / mK or more and 45 W / mK or less. On the other hand, the thermal conductivity of composite material 1 for samples 19 to 24 was 41 W / mK or more and 48 W / mK or less. As shown in Figure 8, the thermal conductivity of composite material 1 for samples 25 and 26 was 46 W / mK or more and 49 W / mK or less. On the other hand, the thermal conductivity of composite material 1 for samples 27 to 32 was 41 W / mK or more and 48 W / mK or less.

[0067] (3-4) In composite material 1 related to tungsten Vickers hardness samples 1, 2, 17, and 25, the strength of tungsten decreased after bonding. This is thought to be due to softening caused by recrystallization of tungsten, as the bonding temperature was high at 1250°C. No significant differences were observed in the other samples.

[0068] From the above results, it was confirmed that by setting the thickness of the embrittlement layer 40 to 3.3 μm or less, a composite material 1 with high bonding strength can be obtained without reducing thermal conductivity or the Vickers hardness of tungsten.

[0069] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

[0070] 1 Composite material, 10 Tungsten layer, 20 Bonding layer, 21 First titanium layer, 22 Second titanium layer, 30 Iron-based metal layer, 40 Brittle layer, 50 Titanium layer, R Radius of curvature, T1 First thickness, T2 Second thickness, T3 Third thickness, T4 Fourth thickness, T5 Fifth thickness, T6 Sixth thickness, θ Central angle.

Claims

1. A composite material comprising a tungsten layer, an iron-based metal layer, and a bonding layer containing titanium and located between the tungsten layer and the iron-based metal layer, wherein the bonding layer includes an embrittlement layer containing carbides, the embrittlement layer is located at the interface between the iron-based metal layer and the bonding layer, and the thickness of the embrittlement layer is 3.3 μm or less.

2. The composite material according to claim 1, wherein the composite material is in the form of a plate.

3. The composite material according to claim 1, wherein the composite material has an arc shape in a cross-section parallel to the lamination direction.

4. The composite material according to any one of claims 1 to 3, wherein the thickness of the bonding layer is 10 μm or more.

5. The composite material according to any one of claims 1 to 4, wherein the Vickers hardness of the tungsten layer is 400 HV or higher.

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