A gradient structure HfB2 / Cu-Hf-B copper-based composite material and its preparation method

Abstract

The present invention provides a gradient-structured HfB2 / Cu-Hf-B copper matrix composite material. The central layer of this gradient composite material is composed of micron-sized HfB2 and the nano-sized Cu5Hf phase formed after the precipitation of Hf. The subsurface layer is composed of micron-sized HfB2, nano-sized HfB2, nano-sized Cu5Hf precipitation phase, and B phase. The surface layer is composed of the B phase, where the B phase increases in a gradient from the inside to the outside, forming a B-gradient copper matrix composite material. The present invention also provides a preparation method for the gradient HfB2 / Cu-Hf-B copper matrix composite material, which specifically includes: gas atomization to prepare the precursor HfB2 / Cu-Hf and Cu-B powders, powder mixing or ball milling according to the ratio, hot pressing sintering, thermomechanical treatment, etc. The copper matrix composite material prepared by the present invention overcomes the problem that the surface layer structure of traditional homogeneous bulk materials is severely damaged and fails during the friction and wear process. By designing a gradient structure with high wear resistance on the surface layer, a copper matrix composite material with high strength in the center and wear resistance on the surface layer is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of copper-based composite materials, and particularly relates to a gradient structure HfB2 / Cu-Hf-B copper-based composite material and a preparation method thereof. Background Art

[0002] Copper-based composite materials have been widely used in the fields of electric power, electronics, aerospace, etc. due to their excellent electrical conductivity, mechanical strength, and wear resistance. However, most of the copper-based composite materials on the market at present are homogeneous structures. Although this structure can perform excellently in a certain specific property, its comprehensive performance often appears insufficient when facing multiple performance requirements. Especially in the application of electrical contact materials, the material not only needs to have high electrical conductivity and strength, but also must have good wear resistance. Obviously, it is very difficult for traditional homogeneous composite materials to meet diverse performance requirements simultaneously.

[0003] For example, in the HfB2 / Cu-Hf composite material in Patent CN 115747557A, although the strength and high-temperature performance of the composite material are significantly improved under the mixing of nano-Cu5Hf precipitation phases and HfB2 ceramic phases, the nano-Cu5Hf precipitation phases are not stable at high temperatures, and the size of the HfB2 ceramic phases is relatively large. The contributions of both to the current-carrying friction performance are relatively limited. Once the surface structure of the homogeneous material is damaged during the friction and wear process, it will seriously affect the service life of the components. In order to solve this limitation of homogeneous composite materials, it is necessary to develop high-performance functionally gradient copper-based composite materials. The design concept of functionally gradient materials is to achieve tissue characteristics matching different performance requirements by consciously changing the component content and spatial distribution of the phases in each gradient layer of the material. The gradient structure design can not only overcome the deficiencies of homogeneous composite materials in comprehensive performance, but also better adapt to complex and changeable working environments, and improve the overall service efficiency and life of the materials. Summary of the Invention

[0004] In order to prepare a gradient copper-based composite material with wear-resistant surface and high-strength center, the present invention designs and prepares a gradient structure HfB2 / Cu-Hf-B copper-based composite material by combining various preparation techniques and microstructure designs, so as to solve the technical problem of low surface wear resistance of traditional homogeneous copper materials in complex environments.

[0005] To achieve the above object, the first aspect of the present invention aims to provide a gradient structure HfB2 / Cu-Hf-B copper-based composite material. Its central layer is composed of micron-sized HfB2 and nano-sized Cu5Hf phase formed after the precipitation of Hf. The subsurface layer is composed of micron-sized HfB2, nano-sized HfB2, nano-sized Cu5Hf precipitation phase and B phase. The surface layer is composed of B phase, where the B phase increases in a gradient from the inside to the outside, forming a B-gradient structure HfB2 / Cu-Hf-B copper-based composite material. For the gradient structure HfB2 / Cu-Hf-B copper-based composite material, calculated according to the sum of mass percentages being 100%, the mass percentage of HfB2 is 0.5-8 wt.%, the mass fraction of B is 0-8 wt.%, the mass fraction of Hf is 0-1.5 wt.%, and the balance is Cu.

[0006] Furthermore, according to the gradient increase of the B phase from the inside to the outside, the B content increases in a gradient from the central layer to the surface layer. Specifically, the ratio of HfB2 / Cu-Hf:Cu-B changes in a gradient from 25:1 to 1:20.

[0007] The second aspect of the present invention aims to provide a method for preparing a gradient structure HfB2 / Cu-Hf-B copper-based composite material, including the following steps:

[0008] Step 1, preparing precursor powder by gas atomization: Weigh each component raw material according to mass percentage, heat the raw materials to obtain an intermediate alloy melt. When the melt reaches the reaction temperature, atomize the intermediate alloy melt on a gas atomization device, and then obtain precursor powders of different systems.

[0009] Step 2, mixing precursor powders in proportion: Mix the precursor powders obtained in Step 1 in different proportions, and then perform powder mixing or ball milling to obtain mixed powders with different B contents.

[0010] Step 3, powder treatment: Lay and pre-press the mixed powders obtained in Step 2 in proportion.

[0011] Step 4, sintering: Perform hot pressing sintering on the sample obtained in Step 3.

[0012] Step 5, thermomechanical treatment: Perform thermomechanical treatment on the sample obtained in Step 4.

[0013] Furthermore, in Step 1, the reaction temperature is set to 1200°C - 1550°C, and the intermediate alloy melt is held for 5 min - 30 min before gas atomization to obtain precursor composite powders of different systems.

[0014] Furthermore, in Step 4, the sintering temperature is 750°C - 1050°C, the holding time is 30 - 90 min, and the sintering pressure is 30 - 50 MPa.

[0015] Further, in step 5, the hot deformation amount is 0-50%, the hot deformation temperature is 500-900 °C, and the room temperature deformation is 0-90%.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] (1) This invention patent combines multiple preparation technologies. By precisely controlling the composition ratios of HfB2, B, Hf, and Cu, and adopting a specific preparation process, a copper-based composite material with a B gradient structure is prepared, and a high-performance copper-based composite material with high strength in the center and wear resistance on the surface layer can be obtained.

[0018] (2) The surface layer of the gradient copper-based composite material of the present invention has excellent wear resistance, with an extremely low friction coefficient during the friction process of 50 N and 200 r / min for 30 min. At the same time, this composite material has excellent mechanical properties after deformation. This material has high strength, high hardness, and good wear resistance, and is suitable for applications in various high-load, high-temperature, and high-speed current-carrying wear-resistant environments. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the gradient structure for the examples.

[0020] Figure 2 It is the friction coefficient curves of Examples 1, 2, and 3.

[0021] Figure 3 It is the SEM microstructure diagram of the gradient structure of Example 5. Detailed Embodiments

[0022] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0023] The present invention provides a gradient structure HfB2 / Cu-Hf-B copper-based composite material. Its central layer is composed of micron HfB2 and the nano Cu5Hf phase formed after the precipitation of Hf. The subsurface layer is composed of micron HfB2, nano HfB2, the nano Cu5Hf precipitation phase, and the B phase. The surface layer is composed of the B phase, where the B phase increases in a gradient from the inside to the outside, forming a gradient structure HfB2 / Cu-Hf-B copper-based composite material. For the gradient structure HfB2 / Cu-Hf-B copper-based composite material, calculated according to the sum of mass percentages of 100%, the mass percentage of HfB2 is: 0.5-8 wt.%, the mass fraction of B is 0-8 wt.%, the mass fraction of Hf is 0-1.5 wt.%, and the balance is Cu.

[0024] Among them, the HfB2 particles are in-situ generated by gas atomization and solid-phase sintering, with two scales of micron and nano. The micron-scale is in-situ generated from the liquid phase, while the nano-scale is obtained by solid-phase in-situ generation; Hf is distributed in the central layer of the material, strengthening by precipitating nano Cu5Hf phase, and also generating nano HfB2 particles with B in the subsurface layer; the B phase is distributed in the subsurface layer and the surface layer. A part of B forms HfB2 particles in-situ with Hf in the solid phase, and the remaining unreacted B elements are evenly distributed. According to the amount of B element reaction, the B content increases in a gradient from the central layer to the surface layer. The B phase is distributed in the surface layer as an anti-friction phase, playing an anti-friction role to improve the friction and wear performance of the copper-based composite material.

[0025] In the preparation process of the gradient-structured copper-based composite material, the Cu raw material is preferably oxygen-free Cu; the Hf raw material is preferably a Cu-Hf intermediate alloy; the B raw material is preferably a Cu-B intermediate alloy. Both the Cu-Hf and Cu-B intermediate alloys are prepared by vacuum induction melting of oxygen-free Cu, pure Hf, and pure B, with a melting temperature of 1200 °C to 1500 °C. First, vacuum is pumped before melting, and the melting process is protected by argon.

[0026] Example 1

[0027] This example discloses a preparation method of a gradient-structured HfB2 / Cu-Hf-B copper-based composite material. The gradient structure is a symmetric gradient structure with 11 gradient layers. The preparation method of this gradient-structured HfB2 / Cu-Hf-B copper-based composite material specifically includes the following steps:

[0028] Step 1, preparing precursor powder by gas atomization: The prepared Cu-Hf and Cu-B intermediate alloys are respectively melted in a gas atomization furnace. When the melt temperature reaches 1300 °C, the two melts are mixed and reacted in a draft tube, and then the mixed melt is gas atomized into HfB2 / Cu-Hf composite powder under high-pressure gas flow. Using the same method, Cu-B alloy powder is prepared;

[0029] Step 2, treating and laying the precursor powder: Mix the HfB2 / Cu-Hf and Cu-B precursor powders in proportions of 25:1, 20:1, 15:1, 10:1, and 5:1 to form 5 different mixed powders, and mix them evenly on a vibrating powder mixer at a frequency of 50 Hz for 4 h. Immediately afterwards, lay the 5 different proportions of mixed powders according to Figure 1 the distribution and layer thickness shown in Example 1 to form a symmetric gradient structure through changes in layer thickness and layer composition. Finally, pre-press the laid mixed powder into a block.

[0030] Step 3, put the pre-pressed block in a graphite crucible for hot-pressing sintering. Before sintering, pump the vacuum degree to be lower than 6.0×10 -3Pa, then start pressurizing, pressurize to 30 MPa within 10 min, then start heating and sintering, heat to 950 °C within 60 min, then keep the temperature for 30 min, then start cooling, and finally obtain the gradient structure HfB2 / Cu-Hf-B copper matrix composite;

[0031] Step 4, hot-roll the composite material obtained in Step 3 by 30% at 900 °C;

[0032] Step 5, further cold-roll the sample in Step 4 by 90% to obtain the final sample.

[0033] The tensile strength of the gradient structure copper matrix composite obtained in this example is 476.3 MPa, and the average friction coefficient is 0.1 after friction for 30 min under the conditions of 50 N and 200 r / min. The friction coefficient curve is as Figure 2 shown, and the wear rate is 0.0041 mg / m.

[0034] Example 2

[0035] This example discloses a preparation method of a gradient structure HfB2 / Cu-Hf-B copper matrix composite.

[0036] Except for the different gradient components from those in Example 1, other preparation processes in this example are the same. The change of the gradient components in this example is as Figure 1 shown in Example 2.

[0037] The tensile strength of the gradient structure copper matrix composite obtained in this example is 490.5 MPa, and the average friction coefficient is 0.27 after friction for 30 min under the conditions of 50 N and 200 r / min, and the wear rate is 0.002 mg / m.

[0038] Example 3

[0039] This example discloses a preparation method of a gradient structure HfB2 / Cu-Hf-B copper matrix composite.

[0040] Except for the different gradient components from those in Example 1, other preparation processes in this example are the same. The change of the gradient components in this example is as Figure 1 shown in Example 3.

[0041] The tensile strength of the gradient structure copper matrix composite obtained in this example is 503.1 MPa, and the average friction coefficient is 0.26 after friction for 30 min under the conditions of 50 N and 200 r / min, and the wear rate is 0.0027 mg / m.

[0042] Example 4

[0043] This example discloses a preparation method of a gradient structure HfB2 / Cu-Hf-B copper matrix composite.

[0044] In addition to the gradient composition being different from that in Example 1, the other preparation processes in this example are the same. The change in the gradient composition of this example is as Figure 1 shown in Example 4.

[0045] The tensile strength of the gradient-structured copper-based composite material obtained in this example is 506.5 MPa. After friction for 30 min under the conditions of 50 N and 200 r / min, the average friction coefficient is 0.22, and the wear rate is 0.0019 mg / m.

[0046] Example 5

[0047] This example discloses a preparation method of a gradient-structured HfB2 / Cu-Hf-B copper-based composite material. The specific steps are as follows:

[0048] In addition to the gradient composition being different from that in Example 1, the other preparation processes in this example are the same. The change in the gradient composition of this example is as Figure 1 shown in Example 5.

[0049] The gradient SEM microstructure of the gradient-structured copper-based composite material obtained in this example is as Figure 3 shown. The central layer is composed of micron HfB2 and nano Cu5Hf precipitation phases. The subsurface layer is composed of micron HfB2, nano HfB2, nano Cu5Hf precipitation phases and B phase. The surface layer is composed of B phase, where the B phase decreases in gradient from the inside to the outside, forming a B-gradient copper-based composite material. The tensile strength of this composite material is 511 MPa. After friction for 30 min under the conditions of 50 N and 200 r / min, the average friction coefficient is 0.19, and the wear rate is 0.0028 mg / m. Under the same experimental conditions, compared with the friction and wear performance of the matrix alloy or this copper material, there is an obvious improvement, as shown in Table 1.

[0050] Table 1 Comparison of friction and wear performance between the composite material of the present invention and other copper materials

[0051]

[0052] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A gradient structure HfB2 / Cu-Hf-B copper-based composite material, characterized in that: The central layer includes micron HfB2 and nano Cu5Hf phase formed after Hf is precipitated, the sub-surface layer includes micron HfB2, nano HfB2, nano Cu5Hf precipitation phase and B phase, the surface layer includes B phase, wherein the B phase increases from the inside to the outside, forming a B gradient structure HfB2 / Cu-Hf-B copper-based composite material, and the B content increases gradually from the central layer to the surface layer, specifically: the precursor powder HfB2 / Cu-Hf:Cu-B ratio of the gradient structure HfB2 / Cu-Hf:Cu-B of the preparation of the gradient structure HfB2 / Cu-Hf-B copper-based composite material changes from 25:1 to 1:20; the mass percentage of HfB2 in the gradient structure HfB2 / Cu-Hf-B copper-based composite material is 0.5 based on the sum of the mass percentages as 100%. ～ 8wt.%, mass fraction of B is 0 ～ 8wt.%, mass fraction of Hf is 0 ～ 1.5wt.%, the balance is Cu.

2. A method for preparing the gradient structure HfB2 / Cu-Hf-B copper-based composite material as claimed in claim 1, characterized in that: The following steps are involved: Step 1, preparing precursor powder by gas atomization: first smelting the prepared Cu-Hf and Cu-B master alloys in a gas atomization furnace respectively, and when the melt reaches the reaction temperature, mixing the two melts in a guide tube for reaction, and then gasifying the mixed melt into HfB2 / Cu-Hf composite material powder under high pressure airflow; using the method of preparing powder by gas atomization, Cu-B alloy powder is prepared; Step 2, mixing the precursor powders: according to the gradient increase of the B phase from the inside to the outside, the B content increases gradually from the center layer to the surface layer, and the ratio of the precursor powder HfB2 / Cu-Hf:Cu-B changes from 25:1 to 1:20; the precursor powders HfB2 / Cu-Hf and Cu-B obtained in step 1 are mixed in different proportions, and then mixed or ball-milled to obtain mixed powders with different B contents; Step 3, powder processing: the mixed powder obtained in step 2 is layered and pre-pressed according to proportion; Step 4, sintering: hot pressing and sintering the sample obtained in step 3; Step 5, thermal deformation treatment: subject the sample obtained in step 4 to thermal deformation treatment.

3. The preparation method according to claim 2, characterized in that: In the step 1, the reaction temperature is set at 1200° C. to 1550° C., the intermediate alloy melt is kept warm for 5 min to 30 min and then atomized to obtain precursor composite powders of different systems.

4. The preparation method according to claim 2, characterized in that: In step 4, the sintering temperature is 750° C. to 1050° C., the holding time is 30 to 90 minutes, and the sintering pressure is 30 to 50 MPa.

5. The preparation method according to claim 2, characterized in that: In step 5, the thermal deformation amount is 0-50%, the thermal deformation temperature is 500-900° C., and the room temperature deformation is 0-90%.

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