Ultrafine-grained W-Mo-Cu composites with Mo element distributed at the W / Cu phase boundary

Abstract

Ultrafine-grained W-Mo-Cu composite materials with Mo elements distributed at the W / Cu phase boundary belong to the fields of W-Cu composite materials and powder metallurgy. The ultrafine-grained W phase is uniformly distributed in the Cu matrix, and the added Mo element is dispersed at the W / Cu phase boundary. The Mo content is 2-10 at.%, and the mass percentage of Cu is 20%-40%. The average W phase size can be controlled in the range of approximately 100-400nm. A preparation technology that can control the content of the added components and distribute the added components at the W / Cu phase boundary has been developed. Through this preparation technology, a new ultrafine-grained W-Mo-Cu composite material with ultrafine W grain size and Mo elements distributed at the phase interface has been obtained. This composite material exhibits excellent comprehensive properties in terms of high-temperature stability, strength, plasticity and electrical conductivity.

Description

Technical Field

[0001] The present invention relates to a method for preparing a novel ultrafine-grained W-Mo-Cu composite material in which Mo elements are distributed at the W / Cu phase boundary by using a solid-liquid mixing method and rapid hot pressing sintering. The prepared ultrafine-grained W-Mo-Cu composite material has excellent comprehensive properties and belongs to the field of W-Cu composite materials and powder metallurgy. Background Art

[0002] W-Cu composite materials are composed of a uniform mixture of W and Cu phases. Since the two phases are neither mutually soluble nor form intermetallic compounds, they are a typical pseudoalloy. W-Cu composite materials have the excellent properties of W, such as high melting point, high hardness, low thermal expansion coefficient, and high thermal conductivity and electrical conductivity of Cu, and exhibit high strength, hardness, electrical conductivity, thermal conductivity, and arc erosion resistance. Based on these advantages, W-Cu composite materials play an irreplaceable and important role in many fields such as electronic information, aerospace, and national defense industry. However, with the rapid development of infrastructure construction such as high-voltage power grids in recent years, higher requirements have been placed on the comprehensive performance of W-Cu composite materials in terms of high-temperature stability, mechanical properties, and electrical conductivity.

[0003] To improve the overall mechanical properties of the material, third components are often added to W-Cu composites to manipulate their microstructure and properties. These third components include alloying elements and particle phases. The primary functions of alloying elements include promoting sintering densification, stabilizing the microstructure, and forming solid solutions or compounds, thereby enhancing mechanical properties such as hardness, compressive strength, and flexural strength. The added hard phase nanoparticles are dispersed throughout the matrix, acting as dispersion strengthening. Furthermore, the hard phase can inhibit interfacial migration and stabilize the composite's microstructure. However, excessive addition of the hard phase can easily lead to agglomeration, negatively impacting the strengthening and microstructural stabilization effects. Furthermore, the solid solution of alloying elements and the addition of the hard phase can also lead to a decrease in the electrical conductivity of the composite. This decrease becomes more pronounced with increasing addition amount, dispersion degree, and distribution range. Therefore, the amount, dispersion degree, and distribution location of the third component are crucial to achieving W-Cu-based composites with excellent overall performance.

[0004] Current research on the introduction of a third component primarily relies on a solid-solid method involving ball milling. This method requires a long time to achieve uniform distribution of the added component within the W-Cu matrix. Prolonged ball milling can easily increase impurity levels, significantly reducing the electrical conductivity of the composite. Even with prolonged mixing, it is difficult to fundamentally address the agglomeration of the added component. Furthermore, for fine powder particles, the solid-solid method struggles to control the distribution of the added component within the powder and the composite after sintering, making it impossible to effectively regulate the content and distribution of the added component as needed. As the initial powder particle size decreases, the number of interfaces in the composite obtained after sintering increases, leading to a corresponding increase in the thermal stability of the interfaces and their contribution to mechanical properties. Therefore, there is an urgent need to develop a method that can achieve uniform distribution of the added component at the W / Cu interface, thereby effectively regulating the stability and mechanical properties of the interface and improving the overall performance of W-Cu-based composites. Summary of the Invention

[0005] To address the challenges of improving the high-temperature stability and matching the mechanical properties with the physical conductivity of W-Cu composite materials, the present invention provides a preparation technology that can effectively control the content of added components and distribute the added components at the W / Cu phase boundary. This preparation technology produces a novel ultrafine-grained W-Mo-Cu composite material with ultrafine W grain size. This composite material exhibits excellent comprehensive properties in terms of high-temperature stability, strength, plasticity, and conductivity.

[0006] The method for preparing a W-Mo-Cu composite material provided by the present invention is characterized by comprising the following steps:

[0007] (1) Pour ultrafine W powder into ammonium molybdate solution, place the mixed solution on a magnetic stirrer and stir it thoroughly, such as at a speed of 120 r / min for 5 min, then transfer the mixed solution to a magnetic stirring constant temperature water bath and continue stirring, the water bath temperature is 70-80 ° C, until it is stirred and dried; the powder obtained above is subjected to H2 reduction in a high temperature tube furnace at a temperature of 800 ° C for 60 min to obtain W-Mo composite powder, and the micron-sized Cu powder and the W-Mo composite powder obtained above are planetarily ball milled at a ball-to-material ratio of 10:1 and a speed of 260-400 r / min. After ball milling for 6-12 h, W-Mo-Cu composite powder is obtained;

[0008] (2) After the W-Mo-Cu composite powder obtained in step (1) is loaded into a graphite mold, sintering is completed in a rapid hot pressing sintering furnace, and vacuum is drawn when the vacuum degree reaches 2×10 -2Pa below, current is passed through to increase the temperature at a rate of 80-100°C / min. The pressure is increased while the temperature is increased until it reaches 90-100 MPa and then maintained constant. When the temperature reaches 950°C, the sample is held for 6-10 minutes. After the holding period, the sample is cooled to room temperature in the furnace, and the pressure is released to remove the prepared product. The prepared product is then subjected to H2 heat treatment in a high-temperature tube furnace at 1100°C for 60 minutes to obtain a product with an ultrafine-grained W phase distributed uniformly in the Cu matrix, and the added Mo element is evenly located at the W / Cu phase boundary.

[0009] In the above step (1), the Mo content in the composite material is 2 to 10 at.%, which has a wide controllable range, and the mass percentage of Cu is 20% to 40%.

[0010] In the above step (2), the sintering temperature and the heat treatment temperature can be adjusted according to the different contents of Mo, so that the composition of the composite material after sintering and heat treatment is consistent with that of the powder.

[0011] (3) The average W phase size in the composite material prepared by rapid hot pressing sintering and H2 heat treatment in the present invention is basically consistent with the initial powder particle size, and can be controlled by different matching of process parameters such as ball-to-material ratio, ball milling speed and ball milling time. That is, the ultrafine grains refer to ultrafine grain W phases, and the average W phase size can be controlled in the range of about 100 to 400 nm.

[0012] The characteristics and technical advantages of this technology are as follows:

[0013] ① The present invention uses a solid-liquid mixing method to prepare W-Mo composite powder. The Mo element is distributed on the surface of the W powder particles. After sintering, the Mo element is uniformly retained at the W / Cu phase boundary. Compared with the solid-solid mixing preparation method, the present invention does not require additional ball milling for the dispersion of the Mo element, thereby improving the purity of the composite material components. ② The Mo element distributed at the phase boundary of the present invention can avoid the coarsening of the W phase size during rapid hot pressing sintering and H2 high-temperature heat treatment, thereby improving the high-temperature stability of the W-Cu composite material structure. Therefore, a bulk composite material with a stable ultrafine structure is prepared by rapid hot pressing sintering and H2 heat treatment. In addition, the Mo element can also improve the bonding properties of the phase boundary. Therefore, the stable microstructure and good phase boundary bonding enable the composite material to obtain excellent mechanical properties. ③ The Mo element in the present invention is only distributed in the area near the phase boundary, avoiding the significant impact of the Mo element on the electrical conductivity of the composite material due to its large distribution in the matrix. Therefore, on the basis of obtaining excellent mechanical properties, a high electrical conductivity can be retained. ④ The W-Mo-Cu composite material prepared by the present invention exhibits an excellent match between mechanical properties and physical conductivity characteristics, and is expected to improve the service performance of W-Cu composite materials in the fields of electrical contacts, welding electrodes, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a microscopic morphology of the W-2% Mo-Cu composite material prepared in Example 1;

[0015] Figure 2 This is a composition distribution diagram of the W-2% Mo-Cu composite material prepared in Example 1;

[0016] Figure 3 This is a microscopic morphology of the W-5% Mo-Cu composite material prepared in Example 2;

[0017] Figure 4 This is a microstructure morphology of the W-10% Mo-Cu composite material prepared in Example 3;

[0018] Figure 5 This is a microstructure morphology of the W-Cu composite material prepared in Comparative Example 1;

[0019] Figure 6 Comparison of the compression properties of the W-Mo-Cu composite materials prepared in Examples 1 to 3 and the W-Cu composite material prepared in Comparative Example 1 at room temperature. DETAILED DESCRIPTION

[0020] The present invention is further explained in the following examples, but the present invention is not limited to the following examples.

[0021] Example 1

[0022] 0.392 g of ammonium molybdate salt was dissolved in excess deionized water to completely dissolve the ammonium molybdate. 20 g of ultrafine W powder was then added to the ammonium molybdate solution and stirred thoroughly on a magnetic stirrer at 120 rpm for 5 min. The mixture was then transferred to a magnetically stirred constant-temperature water bath at 80°C and continued stirring until dry. The resulting powder was reduced with H₂ in a high-temperature tube furnace at 800°C for 60 min to obtain a W-Mo composite powder. 8.663 g of micron-sized Cu powder was then planetarily ball-milled with the W-Mo composite powder at a ball-to-powder ratio of 10:1 at 260 rpm for 6 h to obtain a W-2% Mo-Cu composite powder. The resulting W-2% Mo-Cu composite powder was then placed into a graphite mold and sintered in a rapid hot-pressing sintering furnace. When the vacuum in the sintering chamber reached 2×10 -2Pa, start heating, heating rate is 100 ℃ / min, increase pressure at the same time, keep constant pressure after pressure reaches 100MPa, continue heating to 950 ℃ and keep warm for 6min, after the end of keeping warm, turn off the current and let the sample cool to room temperature with the furnace. Place the sample in a high temperature tube furnace for H2 heat treatment, temperature is 1100 ℃, time is 60min, and finally obtain the sample. The microstructure morphology of the W-2% Mo-Cu bulk composite material prepared in this embodiment is shown in FIG. Figure 1 As shown in Figure 2, the average W grain size in the composite material is 233 nm. Figure 2 As shown in Figure 2, Mo element is mainly distributed at the W / Cu phase boundary. The compression properties of the composite material at room temperature are shown in Figure 2. Figure 6 The compressive yield strength is 1425 MPa, the strain is 11%, and the electrical conductivity of the composite material is 41% IACS.

[0023] Example 2

[0024] 1.014 g of ammonium molybdate salt was dissolved in excess deionized water to completely dissolve the ammonium molybdate. 20 g of ultrafine W powder was then added to the ammonium molybdate solution and stirred thoroughly on a magnetic stirrer at 120 rpm for 5 min. The mixture was then transferred to a magnetically stirred constant-temperature water bath at 70°C and continued stirring until dry. The resulting powder was reduced with H₂ in a high-temperature tube furnace at 800°C for 60 min to obtain a W-Mo composite powder. 9.006 g of micron-sized Cu powder was then planetarily ball-milled with the W-Mo composite powder at a ball-to-powder ratio of 10:1 at 330 rpm for 9 h to obtain a W-5% Mo-Cu composite powder. The resulting W-5% Mo-Cu composite powder was then placed into a graphite mold and sintered in a rapid hot-pressing sintering furnace. When the vacuum in the sintering chamber reached 2 × 10 -2 Pa, start heating, heating rate is 100 ℃ / min, increase pressure at the same time, keep constant pressure after pressure reaches 90MPa, continue heating to 950 ℃ and keep warm for 8 minutes, after the end of keeping warm, turn off the current and let the sample cool to room temperature with the furnace. Place the sample in a high temperature tube furnace for H2 heat treatment, the temperature is 1100 ℃, the time is 60 minutes, and finally obtain the sample. The microstructure morphology of the W-5% Mo-Cu bulk composite material prepared in this embodiment is shown in FIG. Figure 3 As shown in Figure 2, the average W grain size in the composite material is 207 nm. The compression properties of the composite material at room temperature are shown in Figure 2. Figure 6 The compressive yield strength is 1430 MPa at a strain of 10%. The electrical conductivity of the composite material is 40% IACS.

[0025] Example 3

[0026] 2.144 g of ammonium molybdate salt was dissolved in excess deionized water to completely dissolve the ammonium molybdate. 20 g of ultrafine W powder was then added to the ammonium molybdate solution and stirred thoroughly on a magnetic stirrer at 120 rpm for 5 min. The mixture was then transferred to a magnetically stirred constant-temperature water bath at 70°C and continued stirring until dry. The resulting powder was reduced with H₂ in a high-temperature tube furnace at 800°C for 60 min to obtain a W-Mo composite powder. 9.491 g of micron-sized Cu powder was then planetarily ball-milled with the W-Mo composite powder at a ball-to-powder ratio of 10:1 at 400 rpm for 12 h to obtain a W-10% Mo-Cu composite powder. The resulting W-10% Mo-Cu composite powder was then placed into a graphite mold and sintered in a rapid hot-pressing sintering furnace. When the vacuum in the sintering chamber reached 2 × 10 -2 Pa, start heating, heating rate is 100 ℃ / min, increase pressure at the same time, keep constant pressure after pressure reaches 90MPa, continue heating to 950 ℃ and keep warm for 10min, after the end of keeping warm, turn off the current and let the sample cool to room temperature with the furnace. Place the sample in a high temperature tube furnace for H2 heat treatment, the temperature is 1100 ℃, the time is 60min, and finally obtain the sample. The microstructure morphology of the W-10% Mo-Cu bulk composite material prepared in this embodiment is shown in FIG. Figure 4 As shown in Figure 2, the average W grain size in the composite material is 195 nm. The compression properties of the composite material at room temperature are shown in Figure 2. Figure 6 The compressive yield strength is 1480 MPa, the strain is 4.5%, and the electrical conductivity of the composite material is 38% IACS.

[0027] Comparative Example 1

[0028] 20g of ultrafine W powder was poured into deionized water, and the solution was placed on a magnetic stirrer and stirred thoroughly at a speed of 120r / min for 5min. The beaker containing the solution was then transferred to a magnetic stirring constant temperature water bath and continued to stir at a water bath temperature of 80°C until it was stirred dry. The powder obtained above was subjected to H2 reduction in a high-temperature tube furnace at a temperature of 800°C for 60min. 8.571g of micron-sized Cu powder and W powder were planetarily ball milled with a mass ratio of grinding balls to powder of 10:1 and a speed of 260r / min. After ball milling for 6h, W-Cu composite powder was obtained. The obtained W-Cu composite powder was loaded into a graphite mold and then placed in a rapid hot pressing sintering furnace for sintering. When the vacuum degree in the sintering chamber reached 2×10 -2Pa, start heating, heating rate is 100 ℃ / min, increase pressure at the same time, keep constant pressure after pressure reaches 100MPa, continue heating to 950 ℃ and keep warm for 6min, after the end of keeping warm, turn off the current and let the sample cool to room temperature with the furnace. Place the sample in a high temperature tube furnace for H2 heat treatment, the temperature is 1100 ℃, the time is 60min, and finally obtain the sample. The microstructure morphology of the W-Cu bulk composite material prepared in this embodiment is shown in FIG. Figure 5 As shown in Figure 2, the average W grain size in the composite material is 257 nm. The compression properties of the composite material at room temperature are shown in Figure 2. Figure 6 The compressive yield strength is 865 MPa, the strain is 11%, and the electrical conductivity of the composite material is 43% IACS.

Claims

1. A novel ultrafine-grained W-Mo-Cu composite material in which Mo element is distributed at the W / Cu phase boundary, characterized in that: The ultrafine-grained W phase is uniformly distributed in the Cu matrix, and the added Mo element is located at the W / Cu phase boundary. The Mo content in the composite material is 2-10 at.%, and the mass percentage of Cu is 20%-40%. The average W phase size can be controlled in the range of 100-400 nm.

2. A method for preparing the novel ultrafine-grained W-Mo-Cu composite material with Mo element distributed at the W / Cu phase boundary according to claim 1, characterized in that: The following steps are involved: (1) Pour ultrafine W powder into ammonium molybdate solution, place the mixed solution on a magnetic stirrer and stir it thoroughly, then transfer the mixed solution to a magnetic stirring constant temperature water bath and continue stirring at a water bath temperature of 70-80 °C until it is stirred dry; the obtained powder is subjected to H2 reduction in a high temperature tube furnace at a temperature of 800 °C for 60 min to obtain W-Mo composite powder, and the micron-sized Cu powder and the obtained W-Mo composite powder are planetarily ball milled at a ball-to-material ratio of 10:1 and a rotation speed of 260-400 r / min. After ball milling for 6-12 h, W-Mo-Cu composite powder is obtained; (2) After the W-Mo-Cu composite powder obtained in step (1) is loaded into a graphite mold, sintering is completed in a rapid hot pressing sintering furnace, and vacuum is drawn when the vacuum degree reaches 2×10 -2 Pa, current was passed to increase the temperature at a rate of 80~100℃ / min. The pressure was increased while the temperature was rising, and the pressure was kept constant after reaching 90~100 MPa. When the temperature rose to 950℃, it was kept constant for 6~10 min. After the insulation, the sample was cooled to room temperature with the furnace, and then the pressure was released and the prepared product was taken out. The prepared product was subjected to H2 heat treatment in a high-temperature tube furnace at a temperature of 1100℃ for 60 min to obtain the final product. In its microstructure, the ultrafine-grained W phase is uniformly distributed in the Cu matrix, and the added Mo element is located at the W / Cu phase boundary.

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