A metal-based composite contact material with gradient textured interface and its preparation process that is resistant to electrical corrosion

Abstract

This invention discloses an electro-erosion resistant metal-based composite contact material with a gradient textured interface and its preparation process, relating to the technical field of metal-based electrical contact materials for low-voltage electrical appliances. The process includes the following steps: S1. Preparation of surface functional phase precursor: Preparing a preform containing nano-scale zirconium diboride-titanium diboride multiphase precursor clusters as an intermediate raw material for introducing the multiphase reinforcing phase; S2. Gradient preform forming: Preparing a core high-conductivity layer preform, an intermediate gradient transition layer preform, and a surface electro-erosion resistant functional layer preform respectively; wherein, the surface preform is obtained by cold pressing after mixing the surface functional phase precursor with matrix metal powder in a certain proportion. Through the core processes of asynchronous rolling pre-control and segmented gradient annealing, the material texture orientation is directionally controlled, resulting in a core high-conductivity layer. This texture exhibits the lowest lattice scattering probability and the smallest effective electron mass along the electron transport direction.

Description

Technical Field

[0001] This invention relates to the field of metal-based electrical contact materials for low-voltage electrical appliances, specifically to an electro-erosion resistant metal-based composite contact material with a gradient textured interface and its preparation process. Background Technology

[0002] Electrical contacts are the core functional components of electrical switching elements, playing a crucial role in connecting and disconnecting circuits and carrying load current. Their conductivity, resistance to electrolytic corrosion, resistance to welding, and contact stability directly determine the service reliability and service life of electrical systems. With the development trend of high-voltage new energy vehicles and high reliability in aerospace equipment, stringent requirements have been placed on electrical contact materials for "high conductivity, high corrosion resistance, high stability, and long lifespan." Existing materials are no longer sufficient to meet the needs of use under complex operating conditions.

[0003] Currently, the mainstream electrical contact materials in the industry are mainly divided into two major systems: silver-based and copper-based. Typical technical solutions are as follows: Single-element metal contacts have excellent conductivity, but are prone to fusion welding and material spatter loss under repeated arc impacts, resulting in extremely poor resistance to electrical erosion and limiting their use to low-load conditions; Oxide dispersion-reinforced silver-based contacts, such as AgSnO2 and AgCdO contact materials, improve electrical erosion resistance by adding oxide ceramic phases, but the introduction of ceramic phases significantly reduces the conductivity of the matrix, and the ceramic phase has poor wettability with the matrix, making it easy to detach with the molten pool during electrical erosion, failing to form a stable arc barrier. Furthermore, CdO is toxic and its use is restricted by the EU RoHS directive and domestic electrical environmental protection standards; Composite gradient contacts, through a composite design of a surface corrosion-resistant layer and a core conductive layer, achieve a certain balance between conductivity and corrosion resistance, but still have three core defects: First, the performance contradictions cannot be fundamentally reconciled. Existing materials mostly have random textures, making it impossible to optimize performance through crystal orientation. They cannot simultaneously satisfy the dense atomic arrangement required for surface electro-erosion resistance and the low-scattered electron transport path required for high conductivity in the core. There is always a trade-off between conductivity and electro-erosion resistance. Second, interface failure is a prominent issue. The functional layer and the substrate are mechanically or weakly metallurgically bonded, and there are abrupt changes in texture and composition. Under high-frequency arc impact and thermal cycling conditions of -40℃ to 150℃, stress concentration easily occurs at the interface, leading to cracks, delamination, and peeling, resulting in premature contact failure. Third, the effect of reinforcing phase modification is limited. Directly adding ceramic phases easily leads to agglomeration and segregation, resulting in weak bonding with the substrate interface. It cannot effectively pin grain boundaries or suppress grain coarsening under high arc temperatures. After long-term service, the contact resistance fluctuates greatly, and the lifespan decays rapidly.

[0004] Currently used methods in the industry, such as internal oxidation, mechanical alloying, and magnetron sputtering coating, cannot fundamentally solve the above problems. Therefore, developing a composite contact material preparation process that combines high conductivity, high resistance to electrical corrosion, high interfacial bonding strength, and long service life has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an electro-erosion resistant metal-based composite contact material with a gradient textured interface and its preparation process. Through continuous gradient textured interface design, in-situ nano-multiphase enhancement and phase regulation, and integrated metallurgical bonding process, it simultaneously solves the core problems of prominent performance contradictions, easy interface failure, and poor service stability of existing materials.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a process for preparing an electro-erosion resistant metal-based composite contact material with a gradient textured interface, comprising the following steps:

[0008] S1. Preparation of surface functional phase precursor: Prepare a preform containing nano-scale zirconium diboride-titanium diboride composite phase precursor clusters as an intermediate raw material for introducing composite phase reinforcement phase;

[0009] S2. Gradient Preform Forming: A core high-conductivity layer preform, an intermediate gradient transition layer preform, and a surface electro-erosion resistant functional layer preform are prepared separately. The surface preform is formed by cold pressing a mixture of the surface functional phase precursor and matrix metal powder in a specific ratio. The intermediate gradient transition layer preform is divided into three groups according to the surface functional phase precursor mass percentages of 1.5%, 3.0%, and 4.5%. These groups are premixed with matrix metal powder and then stacked from the core to the surface in ascending order of mass percentage, achieving a continuous gradient transition of the reinforcing phase concentration. The core preform is formed by cold pressing a mixture of matrix metal powder and chromium, zirconium, titanium, and rare earth modifiers. The matrix metal is at least one of copper, silver, or a copper-silver alloy.

[0010] S3. Vacuum hot isostatic pressing pre-sintering: The core preform, the intermediate gradient transition layer preform, and the surface electro-erosion resistant functional layer preform are coaxially stacked from the inside to the outside and placed in a vacuum hot isostatic pressing furnace. The preform is held at a vacuum degree ≥1×10^-2 Pa, a sintering temperature of 850℃-950℃, and a pressure of 120MPa-180MPa for 2h-4h to obtain an integrated sintered blank with a density ≥98%.

[0011] S4. Asynchronous large deformation rolling texture pre-control: The integrated sintered billet is preheated to 700℃-800℃ and subjected to multi-pass asynchronous hot rolling with a cumulative deformation of ≥90%. The grain orientation rotation is induced by shear stress to form a texture gradient pre-organization and obtain strip billet.

[0012] S5. Online Gradient Annealing Texture Setting: The strip billet is fed into a segmented temperature-controlled online infrared annealing tunnel for gradient annealing. The tunnel is divided into three independently temperature-controlled sections: the inlet section temperature is 400℃-450℃, the middle section temperature is 550℃-600℃, and the outlet section temperature is 700℃-750℃. The total residence time of the strip in the tunnel is 8s-15s. The tunnel is filled with argon gas for protection. After exiting the tunnel, it is immediately water-quenched and cooled at a rate ≥5×10^2K / s to lock in the gradient texture and nanophase structure.

[0013] S6. Post-processing: The strip blank is punched according to product specifications, surface polished, ultrasonically cleaned and dried to obtain the finished composite contact material.

[0014] Furthermore, the preparation method of the surface functional phase precursor in step S1 includes the following steps:

[0015] P1. By weight percentage, take 82%-88% matrix metal powder, 3%-5% amorphous boron powder, 4%-7% sponge titanium fragments, 4%-6% zirconium hydride powder, and 0.3%-0.6% rare earth modifier. First, mix the matrix metal powder, amorphous boron powder, sponge titanium fragments, and rare earth modifier, place them in a planetary ball mill, and ball mill them at a speed of 400r / min-550r / min for 8h-12h under argon protection to obtain a primary mixed powder with uniform structure and high activity.

[0016] P2. Add zirconium hydride powder to the primary mixed powder and continue ball milling for 1.5h-3h to make the zirconium hydride particles uniformly embedded in the surface of the primary mixed powder, avoiding ineffective decomposition caused by the previous ball milling, and obtain composite powder;

[0017] P3. The composite powder is cold isostatically pressed under a pressure of 400MPa-500MPa to form a cylindrical preform with a density of ≥90%.

[0018] P4. The preform is placed in a vacuum sintering furnace with a vacuum degree higher than 5×10^-3 Pa for segmented reaction sintering: First, the temperature is raised to 550℃-600℃ at a rate of 5℃ / min-10℃ / min and held for 2.5h-4h to induce in-situ decomposition of zirconium hydride to release highly active zirconium atoms. At the same time, the released hydrogen gas removes the oxide film on the powder surface in situ, improving the interface purity; then the temperature is raised to 1050℃-1150℃ and held for 4h-6h to allow highly active zirconium atoms and titanium atoms to combine with amorphous boron powder in situ to generate zirconium diboride-titanium diboride multiphase precursor clusters with an average particle size ≤80nm, thus obtaining the surface functional phase precursor.

[0019] Furthermore, in step S4, the asynchronous speed ratio of the asynchronous hot rolling is 1.15-1.3, the deformation per pass is 15%-25%, the heat preservation between passes is 3-5 minutes, the cumulative deformation is 90%-95%, and argon gas protection is used throughout the rolling process to avoid oxidation of the matrix.

[0020] Furthermore, in step S2, the pressure for cold pressing is 300MPa-400MPa, and the holding time is 30s-60s; in step S5, the length ratio of the three temperature control zones of the online infrared annealing tunnel is 2:3:5, which matches the strip dwell time to ensure the continuity of the texture gradient transition.

[0021] Furthermore, the rare earth modifier is at least one of lanthanum and cerium, used to improve the wettability of the ceramic phase with the matrix, refine the grains, and purify the grain boundaries.

[0022] Furthermore, the base metal is oxygen-free electrolytic copper or ultrafine silver powder, which can be flexibly selected according to the cost and performance requirements of the application scenario.

[0023] Secondly, the present invention provides a metal-based composite contact material with a gradient textured interface that is resistant to electrical corrosion. It is prepared by the above-mentioned process and has an integrated metallurgically combined three-layer gradient structure, consisting of a core high conductivity layer, an intermediate gradient transition layer, and a surface resistant electrical corrosion functional layer from the inside to the outside.

[0024] The chemical composition of the composite contact material, by weight percentage, is as follows: zirconium diboride-titanium diboride composite reinforcing phase: 2.0%-5.0%; chromium: 0.5%-1.2%; zirconium: 0.3%-0.8%; titanium: 0.2%-0.6%; rare earth modifier: 0.1%-0.3%; the balance being a face-centered cubic matrix metal and unavoidable impurities, wherein the total content of unavoidable impurities is ≤0.1%.

[0025] The zirconium diboride-titanium diboride composite reinforcing phase is dispersed in the grain boundaries of the surface electro-erosion resistant functional layer in the form of nanoparticles with an average particle size ≤80nm. It also exhibits a concentration gradient increasing along the core to the surface in the intermediate gradient transition layer. The composite reinforcing phase is absent in the core high conductivity layer.

[0026] The composite contact material has a continuous gradient textured interface: the texture occupancy of the core high conductivity layer is ≥70%; the texture occupancy of the surface electro-erosion resistant functional layer is ≥75%; the texture of the intermediate gradient transition layer is a continuous linear gradient transition from the core high conductivity layer to the surface electro-erosion resistant functional layer, without any abrupt textured interface.

[0027] The texture occupancy rate was tested using GB / T36165-2018 "Electron Backscatter Diffraction (EBSD) Test Method for Metallic Materials". The test conditions were: accelerating voltage 20kV, step size 0.5μm, test area not less than 300μm×300μm, and texture occupancy rate was calculated based on the grain volume fraction with orientation difference ≤15°.

[0028] Furthermore, the core high conductivity layer accounts for 70%-85% of the total thickness, the intermediate gradient transition layer accounts for 5%-10% of the total thickness, and the surface electro-erosion resistant functional layer accounts for 10%-20% of the total thickness. The thickness ratio of each layer can be flexibly adjusted according to the rated voltage and current conditions.

[0029] Furthermore, the average particle size of the zirconium diboride-titanium diboride composite reinforcing phase is 50nm-80nm. The particle size is tested according to GB / T38532-2020 "Method for Measurement of Average Particle Size and Particle Size Distribution of Nanoparticles by Microbeam Analysis and Transmission Electron Microscopy", and the analytic average particle size is calculated by randomly selecting no less than 100 particles.

[0030] Furthermore, when the base metal is oxygen-free electrolytic copper, the conductivity of the composite contact material is ≥85% IACS; when the base metal is ultrafine silver powder, the conductivity of the composite contact material is ≥95% IACS.

[0031] Furthermore, the interfacial bonding strength of the composite contact material is ≥320MPa, and the contact resistance fluctuation amplitude after 100,000 AC220V / 20A breaking tests is ≤8%.

[0032] Compared with existing technologies, this invention provides an electro-erosion resistant metal-based composite contact material with a gradient textured interface and its preparation process, which has the following beneficial effects: Through the core processes of asynchronous rolling pre-control and segmented gradient annealing, the material texture orientation is directionally controlled, so that a high conductivity core layer is formed in the core. This texture has the lowest lattice scattering probability and the smallest effective electron mass along the electron transport direction, and the conductivity is 12%-15% higher than that of conventional random textured materials of the same composition; an electro-erosion resistant functional layer is formed on the surface. This texture is the densest atomic close-packed surface of face-centered cubic metal, with the highest atomic binding energy. The resistance to arc welding and the resistance to material loss are more than twice that of conventional materials, which fundamentally alleviates the industry pain point of the trade-off between conductivity and corrosion resistance of existing materials.

[0033] Through an integrated process of composition gradient prefabrication and texture gradient control, the texture, reinforcing phase concentration, mechanical properties, and thermal expansion coefficient of the intermediate gradient transition layer are all continuously and linearly transitioned, with no obvious interface or stress concentration. The interface bonding strength is ≥320MPa, matching the strength of the matrix. After 100,000 high-frequency arc impacts and thermal cycling from -40℃ to 150℃, there are no cracks, delamination, or peeling. This completely solves the core problem of easy failure of the interface of existing composite contacts, and significantly improves the reliability of service.

[0034] Through a segmented in-situ decomposition-combination process of zirconium hydride, a zirconium diboride-titanium diboride composite reinforcing phase with an average particle size ≤80nm is generated in situ within the matrix, avoiding the agglomeration and segregation problems caused by directly adding ceramic powder. Combined with rare earth modification, the wetting angle between the ceramic phase and the matrix is ​​≤45°, significantly improving interfacial bonding. The nano-composite particles precisely pin grain boundaries, suppressing grain boundary migration and grain coarsening under high arc temperatures. After 100,000 breaking cycles, the contact resistance fluctuation is ≤8%, demonstrating excellent long-term service stability.

[0035] By using prefabricated gradient proportioning, asynchronous large deformation rolling texture pre-control, and online gradient annealing texture shaping, precise control of texture orientation and reinforcing phase distribution is achieved, with a yield of ≥95%. It can mass-produce strips and stamped contact parts of different thicknesses and specifications, and the production cost is reduced by more than 40% compared with similar imported products, which has extremely high industrial application value. Detailed Implementation

[0036] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention provides a technical solution for an electro-erosion resistant metal-based composite contact material with a gradient textured interface and its preparation process:

[0038] Example 1: This example provides a preparation process for a copper-based composite contact material with a gradient textured interface that is resistant to electrical corrosion, and the resulting composite contact material. The specific steps are as follows:

[0039] Preparation of surface functional phase precursors

[0040] Prepare the following raw materials by weight percentage: 85.0% electrolytic copper powder (particle size 50μm), 4.0% amorphous boron powder, 5.5% sponge titanium scrap, 5.0% zirconium hydride powder, and 0.5% metallic cerium powder.

[0041] The specific preparation steps are as follows:

[0042] (1) The electrolytic copper powder, amorphous boron powder, sponge titanium scrap and metallic cerium powder in the above proportion are mixed and placed in a planetary ball mill. Under argon protection, they are ball-milled at a speed of 500 r / min for 10 h to obtain primary mixed powder.

[0043] (2) Add the measured amount of zirconium hydride powder to the ball mill jar and continue ball milling for 2 hours to obtain composite powder;

[0044] (3) The composite powder is placed in a steel mold and cold isostatically pressed under a pressure of 450MPa to form a cylindrical preform with a diameter of 30mm and a density of 92%.

[0045] (4) The preform is placed in a vacuum sintering furnace with a vacuum degree of 3×10^-3Pa for segmented reaction sintering: in the first stage, the temperature is raised to 580℃ at a rate of 8℃ / min and held for 3h to induce in-situ decomposition of zirconium hydride; in the second stage, the temperature is raised to 1100℃ and held for 5h to generate in-situ zirconium diboride-titanium diboride multiphase precursor clusters with an average particle size of about 65nm, thus obtaining the surface functional phase precursor.

[0046] Preparation of composite contact materials

[0047] The chemical composition of the finished product by weight percentage is as follows: 3.2% zirconium diboride-titanium diboride composite reinforcing phase, 0.8% chromium, 0.5% zirconium, 0.4% titanium, 0.2% metallic cerium, with the balance being electrolytic copper and unavoidable impurities, and the total impurity content being ≤0.1%.

[0048] The specific preparation process is as follows:

[0049] (1) Gradient preform molding: Core, transition layer and surface preforms were prepared separately. The core preform was made by mixing electrolytic copper powder with chromium, zirconium, titanium and metallic cerium, and then cold-pressed under 350 MPa pressure for 45 s. The intermediate gradient transition layer preform was divided into three groups according to the proportion of surface functional phase precursor of 1.5%, 3.0% and 4.5%, and was premixed with electrolytic copper powder respectively. The preforms were then stacked and cold-pressed from the core to the surface in order of increasing proportion. The surface preform was made by mixing surface functional phase precursor and electrolytic copper powder in a certain proportion and then cold-pressing.

[0050] (2) Vacuum hot isostatic pressing pre-sintering: The three-layer preform is coaxially stacked from the inside to the outside and placed in a vacuum hot isostatic pressing furnace. Under the conditions of vacuum degree 8×10^-3Pa, temperature 900℃ and pressure 150MPa, it is held at temperature and pressure for 3h to obtain an integrated sintered blank with a density of 98.5%;

[0051] (3) Asynchronous large deformation rolling texture pre-control: The sintered billet is preheated to 750℃ and subjected to multi-pass asynchronous hot rolling with an asynchronous speed ratio of 1.2, a single-pass deformation of 20%, and a 4-minute heat preservation between passes, resulting in a cumulative deformation of 92%. Argon gas protection is used throughout the process to obtain strip billet.

[0052] (4) Online gradient annealing texture shaping: The strip billet is fed into the segmented temperature-controlled infrared annealing tunnel. The length ratio of the three temperature control zones in the tunnel is 2:3:5. The temperature of the inlet section is 420℃, the temperature of the middle section is 580℃, and the temperature of the outlet section is 720℃. The total residence time of the strip is 12s. The tunnel is filled with argon gas for protection. After exiting, it is immediately water quenched and cooled at a rate of 8×10^2K / s.

[0053] (5) Post-processing: The strip is punched, polished, ultrasonically cleaned and dried to obtain the finished composite contact material with a total thickness of 0.8 mm, of which the core thickness is 0.6 mm, the transition layer thickness is 0.06 mm and the surface layer thickness is 0.14 mm.

[0054] Example 2, preparation of surface functional phase precursor: The raw materials by weight percentage are 88.0% electrolytic copper powder, 3.0% amorphous boron powder, 4.0% sponge titanium fragments, 4.0% zirconium hydride powder, and 1.0% metallic lanthanum powder; in step (4), the first stage is heated to 550℃ and held for 4h; the second stage is heated to 1050℃ and held for 6h to generate a multiphase precursor cluster with an average particle size of about 58nm;

[0055] Chemical composition of the finished product: 2.0% zirconium diboride-titanium diboride composite reinforcing phase, 0.5% chromium, 0.3% zirconium, 0.2% titanium, 0.1% metallic lanthanum, with the balance being electrolytic copper and unavoidable impurities, the total impurity content being ≤0.1%;

[0056] Preparation process: Step (2) Pre-sintering temperature 850℃, pressure 120MPa, heat and pressure holding for 4h; Step (3) Rolling temperature 700℃, asynchronous speed ratio 1.15, cumulative deformation 90%; Step (4) Annealing tunnel entrance section 400℃, middle section 550℃, exit section 700℃, residence time 15s;

[0057] Finished product dimensions: Total thickness 0.8mm, core thickness 0.68mm, transition layer thickness 0.04mm, surface layer thickness 0.08mm;

[0058] The rest is the same as in Example 1.

[0059] Example 3, preparation of surface functional phase precursor: The raw materials by weight percentage are 82.0% ultrafine silver powder, 5.0% amorphous boron powder, 7.0% sponge titanium fragments, and 6.0% zirconium hydride powder; Step (1) Ball milling speed 450 r / min, ball milling time 12 h; Step (4) First stage heating to 600℃, holding for 2.5 h; Second stage heating to 1150℃, holding for 4 h, generating a multiphase precursor cluster with an average particle size of about 72 nm;

[0060] The chemical composition of the finished product is as follows: 5.0% zirconium diboride-titanium diboride composite reinforcing phase, 1.2% chromium, 0.8% zirconium, 0.6% titanium, 0.3% metallic cerium, with the balance being ultrafine silver powder and unavoidable impurities, the total impurity content being ≤0.1%;

[0061] Preparation process: Step (2) Pre-sintering temperature 950℃, pressure 180MPa, heat and pressure holding for 2h; Step (3) Rolling temperature 800℃, asynchronous speed ratio 1.3, cumulative deformation 95%; Step (4) Annealing tunnel entrance section 450℃, middle section 600℃, exit section 750℃, residence time 8s;

[0062] Finished product dimensions: Total thickness 0.5mm, core thickness 0.35mm, transition layer thickness 0.05mm, surface layer thickness 0.10mm;

[0063] The rest is the same as in Example 1.

[0064] Example 4, Preparation of surface functional phase precursor: The raw materials, by weight percentage, are 84.0% copper-silver alloy powder (Cu80Ag20), 4.5% amorphous boron powder, 6.0% sponge titanium fragments, 5.0% zirconium hydride powder, and 0.5% metallic cerium powder;

[0065] The chemical composition of the finished product is as follows: 2.8% zirconium diboride-titanium diboride composite reinforcing phase, 0.9% chromium, 0.6% zirconium, 0.5% titanium, 0.2% metallic cerium, and the balance being copper-silver alloy and unavoidable impurities, with a total impurity content of ≤0.1%.

[0066] The rest is the same as in Example 1.

[0067] Comparative Example 1: No gradient texture control was performed. The preparation process adopted conventional powder metallurgy sintering + synchronous rolling, without asynchronous rolling texture pre-control and online gradient annealing steps. The remaining parameters were the same as those in Example 1.

[0068] Comparative Example 2 provides a preparation process for a gradient textured copper-based contact material without a nano-multiphase reinforcing phase. The finished product does not contain a zirconium diboride-titanium diboride multiphase reinforcing phase in its chemical composition, and the remaining matrix components are completely consistent with those in Example 1. The preparation process is also completely consistent with that in Example 1.

[0069] Comparative Example 3 provides a preparation process for a composite contact material without an intermediate gradient transition layer. The chemical composition of the finished product is completely consistent with that of Example 1. The difference is that there is no intermediate gradient transition layer, the surface preform and the core preform are directly stacked and sintered, and the texture has no transition. The other preparation parameters are consistent with those of Example 1.

[0070] Comparative Example 4 provides a preparation process for a composite contact material by directly adding a commercial ceramic phase. The chemical composition of the finished product is completely consistent with that of Example 1. The difference is that: no surface functional phase precursor is prepared, and the same amount of commercial zirconium diboride and titanium diboride ceramic powder is directly added to the matrix. The other preparation parameters are consistent with those of Example 1.

[0071] Comparative Example 5: This comparative example is a commercially available mainstream AgSnO2 contact material, purchased from a major domestic electrical contact material manufacturer. It has a silver content of 88%, a SnO2 content of 12%, and a thickness of 0.8 mm, and serves as a control group for existing technologies.

[0072] Performance Testing and Results Analysis

[0073] The contact materials prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were selected and prepared into standard samples. All samples underwent performance testing using current valid national standards. The testing methods are as follows:

[0074] Conductivity test: Refer to GB / T3048.2-2024 "Test methods for electrical properties of wires and cables - Part 2: Test for resistivity of metallic materials", test the resistivity of the sample and convert it to conductivity (%IACS);

[0075] Interface bond strength test: Refer to GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature", and use the transverse tensile method to test the interface bond strength;

[0076] Electrolytic corrosion resistance test: Referring to GB / T21711.1-2008 "Basic electromechanical relays Part 1: General Specification", a relay life test bench with AC220V and rated current of 20A was used to conduct 100,000 breaking tests to test the mass loss of the sample, the fluctuation range of contact resistance, and to observe whether welding or delamination occurs.

[0077] Texture testing: Refer to GB / T36165-2018 "Electron Backscatter Diffraction (EBSD) Test Method for Metallic Materials". The test conditions are: accelerating voltage 20kV, step size 0.5μm, test area 300μm×300μm, and the texture occupancy rate is calculated based on the grain volume fraction with an orientation difference ≤15°.

[0078] Nanoparticle size testing: Referring to GB / T38532-2020 "Microbeam analysis - Transmission electron microscopy - Measurement method of average particle size and particle size distribution of nanoparticles", transmission electron microscopy was used to test the particle size distribution of 100 randomly selected particles. The analytical average particle size was calculated.

[0079] The performance test results are shown in Tables 1 and 2:

[0080] Table 1

[0081] Corresponding group Conductivity (%IACS) Interfacial bonding strength (MPa) Mass loss (mg) after 100,000 fracturing cycles Example 1 86.2 360 1.8 Example 2 88.5 335 2.4 Example 3 96.8 390 1.2 Example 4 82.3 375 1.6 Comparative Example 1 75.1 310 4.2 Comparative Example 2 90.5 330 6.5 Comparative Example 3 85.8 180 3.5 Comparative Example 4 71.2 245 4.8 Comparative Example 5 (Commercially Available) 76.5 260 3.8

[0082] Table 2

[0083] Corresponding group Core high conductivity layer texture occupancy Surface electro-erosion resistant functional layer texture occupancy Average particle size of the reinforcing phase (nm) Example 1 76% 81% 65 Example 2 72% 77% 58 Example 3 78% 83% 72 Example 4 74% 79% 68 Comparative Example 1 22% 28% 65 Comparative Example 2 75% 80% - Comparative Example 3 76% 81% 65 Comparative Example 4 71% 76% 260 Comparative Example 5 (Commercially Available) 25% 30% 800

[0084] Based on the above test data, the following conclusions can be drawn: Examples 1 to 4 simultaneously achieved high conductivity and high resistance to electrolytic corrosion. The conductivity of the copper-based system was ≥82% IACS, and that of the silver-based system reached 96.8% IACS, which is far higher than that of randomly textured materials of the same composition and commercially available AgSnO2 contacts. The mass loss after 100,000 breaks was ≤2.4mg, which is only 31%-63% of that of commercially available products, and the contact resistance fluctuation was ≤5.8%, verifying the synergistic optimization effect of the preparation process of this invention on material performance.

[0085] Comparative Example 1, using a conventional random textured process, showed a 12.9% decrease in conductivity compared to Example 1, and a significant reduction in electro-erosion resistance, demonstrating the decisive role of the asynchronous rolling + gradient annealing texture control process of this invention in material performance. Comparative Example 2, without the addition of a nano-complex reinforcing phase, exhibited excellent conductivity but lacked the arc barrier and grain boundary pinning effect of the nano-phase, resulting in extremely poor electro-erosion resistance. Severe fusion welding occurred after 100,000 cycles of breaking, demonstrating the core role of in-situ generation of the nano-complex reinforcing phase in this invention.

[0086] Comparative Example 3, without an intermediate gradient transition layer, had an interfacial bonding strength of only 180 MPa, a 50% decrease compared to Example 1. Obvious interfacial cracks appeared after the fracture test, demonstrating the core role of the gradient preform forming process of this invention in eliminating interfacial stress concentration and improving bonding strength. Comparative Example 4, with the direct addition of commercial ceramic powder, resulted in severe agglomeration of the reinforcing phase, with an average particle size of 260 nm. Both conductivity and resistance to electrolytic corrosion deteriorated significantly, verifying the technical advantages of this invention in preparing nano-precursors through in-situ segmented reaction sintering.

[0087] Compared to the closest existing technology, Comparative Example 5 (commercially available mainstream AgSnO2 contacts), Embodiment 1 of the present invention has a 12.7% increase in conductivity, a 52.6% reduction in mass loss after 100,000 breaking cycles, a 38.5% increase in interfacial bonding strength, and an 82.1% reduction in contact resistance fluctuation.

[0088] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A preparation process for an electro-erosion resistant metal-based composite contact material with a gradient textured interface, characterized in that: Includes the following steps: S1. Prepare a preform containing nano-scale zirconium diboride-titanium diboride composite precursor clusters as an intermediate raw material for introducing composite reinforcing phases; S2. Prepare a core high-conductivity layer preform, an intermediate gradient transition layer preform, and a surface electro-erosion resistant functional layer preform, respectively; wherein, the surface preform is prepared by cold pressing after mixing the surface functional phase precursor with matrix metal powder in a certain proportion; the intermediate gradient transition layer preform is divided into three groups according to the mass ratio of surface functional phase precursor of 1.5%, 3.0%, and 4.5%, respectively, and is premixed with matrix metal powder, and then stacked and cold pressed from the core to the surface in order of increasing proportion to achieve a continuous gradient transition of reinforcing phase concentration; the core preform is prepared by cold pressing after mixing matrix metal powder with chromium, zirconium, titanium, and rare earth modifier; the matrix metal is at least one of copper, silver, or copper-silver alloy; S3. The core preform, the intermediate gradient transition layer preform, and the surface electro-erosion resistant functional layer preform are coaxially stacked from the inside to the outside and placed in a vacuum hot isostatic pressing furnace. The furnace is held at a vacuum degree ≥1×10^-2 Pa, a sintering temperature of 850℃-950℃, and a pressure of 120MPa-180MPa for 2h-4h to obtain an integrated sintered blank with a density ≥98%. S4. Preheat the integrated sintered billet to 700℃-800℃ and perform multi-pass asynchronous hot rolling. The cumulative deformation is ≥90%. The grain orientation rotation is induced by shear stress to form a pre-structure with texture gradient, and the strip billet is obtained. S5. The strip billet is fed into a segmented temperature-controlled online infrared annealing tunnel for gradient annealing. The tunnel is divided into three independently temperature-controlled sections: the inlet section temperature is 400℃-450℃, the middle section temperature is 550℃-600℃, and the outlet section temperature is 700℃-750℃. The total residence time of the strip in the tunnel is 8s-15s. The tunnel is filled with argon gas for protection. After exiting the tunnel, it is immediately water-quenched and cooled at a rate ≥5×10^2K / s to lock in the gradient texture and nanophase structure. S6. The strip blank is punched according to the product specifications, the surface is polished, ultrasonically cleaned and dried to obtain the finished composite contact material.

2. The preparation process of an electro-erosion resistant metal-based composite contact material with a gradient textured interface according to claim 1, characterized in that: The preparation method of the surface functional phase precursor in step S1 includes the following steps: P1. By weight percentage, take 82%-88% matrix metal powder, 3%-5% amorphous boron powder, 4%-7% sponge titanium fragments, 4%-6% zirconium hydride powder, and 0.3%-0.6% rare earth modifier. First, mix the matrix metal powder, amorphous boron powder, sponge titanium fragments, and rare earth modifier, place them in a planetary ball mill, and ball mill them at a speed of 400r / min-550r / min for 8h-12h under argon protection to obtain the primary mixed powder. P2. Add zirconium hydride powder to the primary mixed powder and continue ball milling for 1.5h-3h to obtain composite powder; P3. The composite powder is cold isostatically pressed under a pressure of 400MPa-500MPa to form a preform with a density of ≥90%. P4. The preform is placed in an environment with a vacuum degree higher than 5×10^-3Pa for segmented reaction sintering: first, the temperature is raised to 550℃-600℃ at a rate of 5℃ / min-10℃ / min and held for 2.5h-4h to induce the in-situ decomposition of zirconium hydride to release highly active zirconium atoms; then the temperature is raised to 1050℃-1150℃ and held for 4h-6h to generate nanoscale zirconium diboride-titanium diboride multiphase precursor clusters in situ, thus obtaining the surface functional phase precursor.

3. The preparation process of an electro-erosion resistant metal-based composite contact material with a gradient textured interface according to claim 1, characterized in that: In step S4, the asynchronous speed ratio of the asynchronous hot rolling is 1.15-1.3, the deformation per pass is 15%-25%, the heat preservation between passes is 3-5 minutes, the cumulative deformation is 90%-95%, and argon gas protection is used throughout the rolling process.

4. The preparation process of an electro-erosion resistant metal-based composite contact material with a gradient textured interface according to claim 1, characterized in that: The pressure for cold pressing in step S2 is 300MPa-400MPa, and the holding time is 30s-60s; the length ratio of the three temperature control zones of the online infrared annealing tunnel in step S5 is 2:3:5, which matches the strip dwell time.

5. The preparation process of an electro-erosion resistant metal-based composite contact material with a gradient textured interface according to claim 1, characterized in that: The rare earth modifier is at least one of lanthanum and cerium.

6. A metal-based composite contact material with a gradient textured interface, characterized in that, The composite contact material is prepared by the preparation process described in any one of claims 1-5. The composite contact material is an integrated metallurgically combined three-layer gradient structure, consisting of a core high conductivity layer, an intermediate gradient transition layer, and a surface electro-erosion resistant functional layer from the inside out. The chemical composition of the composite contact material, by weight percentage, is: zirconium diboride-titanium diboride composite reinforcing phase: 2.0%-5.0%; Chromium: 0.5%-1.2%; Zirconium: 0.3%-0.8%; Titanium: 0.2%-0.6%; Rare earth modifier: 0.1%-0.3%; Balance: face-centered cubic matrix metal and unavoidable impurities, the total content of said unavoidable impurities ≤0.1%; The zirconium diboride-titanium diboride composite reinforcing phase is dispersed in the grain boundaries of the surface electro-erosion resistant functional layer in the form of nanoparticles with an average particle size ≤80nm. It also exhibits a concentration gradient increasing along the core to the surface in the intermediate gradient transition layer. The composite reinforcing phase is absent in the core high conductivity layer. The composite contact material has a continuous gradient textured interface: the texture occupancy of the core high conductivity layer is ≥70%; the texture occupancy of the surface electro-erosion resistant functional layer is ≥75%; the texture of the intermediate gradient transition layer transitions continuously and linearly from the core high conductivity layer to the surface electro-erosion resistant functional layer, without any abrupt texture changes.

7. The composite contact material according to claim 6, characterized in that, The core high conductivity layer accounts for 70%-85% of the total thickness, the intermediate gradient transition layer accounts for 5%-10% of the total thickness, and the surface electro-erosion resistant functional layer accounts for 10%-20% of the total thickness; the average particle size of the zirconium diboride-titanium diboride composite reinforcing phase is 50nm-80nm.

8. When the base metal is oxygen-free electrolytic copper, the conductivity of the composite contact material is ≥85% IACS; when the base metal is ultrafine silver powder, the conductivity of the composite contact material is ≥95% IACS.

9. The composite contact material according to claim 6, characterized in that, The interfacial bonding strength of the composite contact material is ≥320MPa, and the contact resistance fluctuation after 100,000 AC220V / 20A breaking tests is ≤8%.