High-strength high-conductivity lamellar heterogeneous copper-chromium-zirconium alloy and preparation method thereof

Abstract

The invention discloses a preparation method of a high-strength and high-conductivity lamellar heterogeneous copper-chromium-zirconium alloy, and belongs to the technical field of preparation and modification of copper alloy materials. According to the method, equal channel angular pressing (ECAP) and an accumulative ply rolling process are combined, CuCrZr alloy subjected to solid solution state and different passes of ECAP treatment is sliced, overlaid, fixed and subjected to one-time ply rolling, metallurgical bonding of the two layers of alloy is achieved, the steps are repeated on metal sheets subjected to ply rolling, accumulative ply rolling can be carried out multiple times, and finally annealing treatment is carried out again. According to the process, an ideal lamellar heterogeneous structure with alternate coarse and fine crystals can be obtained by controlling the size of crystal grains in each layer of alloy, meanwhile, the deformation far larger than that of common rolling can be obtained through multi-pass accumulative ply rolling, the crystal grains are refined to the nanoscale, meanwhile, the influence of a high-density crystal boundary on the electric conductivity is balanced, the tensile strength and the electric conductivity are synchronously improved, and the service life of the alloy is prolonged. The deformation aging process is far beyond the conventional deformation aging process.

Description

Technical Field

[0001] The present invention belongs to the technical field of copper alloy preparation and modification, and in particular relates to a high-strength and high-conductivity layered heterogeneous copper alloy and a preparation method thereof. Background Art

[0002] High-strength, high-conductivity copper alloys are a class of structural and functional materials with ultra-high strength and excellent electrical conductivity. They are primarily used in integrated circuit lead frames, electrified railway contact wires, high-intensity magnetic field conductors, high-power asynchronous traction motor rotors, rocket engine linings, resistance welding electrodes, and contact materials. They are key materials supporting modern power electronics and major national engineering projects. With the continuous advancement of science and technology and modern industry, higher requirements are being placed on the mechanical and electrical properties of copper alloys. For example, with the development of integrated circuits towards large and ultra-large scale, lead frame copper strips are required to have a tensile strength exceeding 600 MPa, an electrical conductivity greater than 80% IACS, and a high-temperature softening temperature greater than 527°C. The development of high-speed railway transportation requires that locomotive contact wires have a room-temperature tensile strength between 600 and 700 MPa and an electrical conductivity between 80 and 95% IACS.

[0003] At present, the common methods for improving the strength of copper alloys are mainly severe plastic deformation and solution aging treatment. Severe plastic deformation includes rolling, equal channel angular pressing, cumulative rolling and high-pressure torsion. It is through plastic deformation that a large number of dislocations and twins are produced in the alloy, that is, work hardening. At the same time, it can also refine the grains to improve the strength and hardness of the copper alloy. However, fine grain strengthening and work hardening have limited effects on the strength improvement of copper, and will inevitably introduce defects, increase the scattering of electrons by the alloy matrix, and thus have an adverse effect on the electrical conductivity of the alloy. Therefore, how to coordinate the contradictory relationship between strength and conductivity and achieve the best match between the strength and electrical conductivity of the material has become an important research topic in the preparation of high-performance copper alloys.

[0004] Unlike conventional homogeneous materials, layered heterogeneous materials exhibit a simultaneous improvement in both strength and ductility due to the large strain gradients generated near the interfaces of the soft and hard structural units, resulting in back stress hardening. As a type of heterogeneous material, layered heterogeneous metals also possess many other excellent properties, such as low dislocation and grain boundary densities in the coarse-grained layers, which minimize electron scattering and effectively improve the overall electrical conductivity of the alloy while maintaining high strength. The excellent comprehensive properties of layered heterogeneous materials provide a new approach for the preparation of high-strength and high-conductivity copper alloys. Summary of the Invention

[0005] This invention addresses the shortcomings of existing processes by providing a novel high-strength, high-conductivity, layered heterogeneous copper alloy and its preparation method. This alloy utilizes equal channel angular pressing (ECAP) to refine grains to varying sizes, combined with a cumulative roll-bonding process to produce a layered heterogeneous structure with interphases of coarse and fine grains. This alloy achieves an effective combination of high strength (664-789 MPa) and high conductivity (74%-89% IACS).

[0006] The present invention first provides a high-strength, high-conductivity layered heterogeneous copper alloy with a nanostructured structure comprising multiple layers of alternating coarse and fine nanocrystals and dispersed nanoprecipitates. The nanoprecipitates are ≤40 nm in size. The grain size in the coarse-grained region is ≤45 μm, and the grain size in the fine-grained region is ≤205 nm.

[0007] The present invention further provides a method for preparing the above-mentioned high-strength and high-conductivity layered heterogeneous copper alloy, comprising the following steps: (1) Solution treatment: The CuCrZr alloy is placed in a resistance furnace for solution treatment. The purpose is to obtain a supersaturated solid solution with coarse grains, which is convenient for subsequent plastic deformation and the acquisition of grains of different sizes. The specific process is to heat the alloy to 950-1000 °C and keep it at this temperature for 0.5-1 h at a heating rate of 5 °C / min. Then, the alloy is quickly placed in a 5 wt.% NaCl solution to cool it down. Finally, the black oxide layer on the surface of the alloy is polished off.

[0008] The composition of the CuCrZr alloy by mass ratio is Cr: 0.95-1.06%, Zr: 0.08-0.12%, trace amounts of impurities such as Fe, Zn, and P, and the balance is Cu.

[0009] (2) Equal Angular Extrusion: The alloy treated in step (1) was subjected to different passes of equal angular extrusion (ECAP) at room temperature to obtain copper alloy bars with different grain sizes, which were used as coarse-grained or fine-grained layers of the layered heterogeneous alloy. The extrusion speed of ECAP was 15 mm / min, the extrusion temperature was room temperature, the die had an inner angle of 110°, an outer angle of 0°, an inner diameter of 12 mm × 12 mm, and the lubricant was a mixture of MoS2 and engine oil in a ratio of (2:1).

[0010] In some exemplary embodiments of the present invention, the ECAP has 0 to 4 extrusion passes, such as 0, 2, and 4 passes. As the number of extrusion passes increases, the grain size gradually becomes finer.

[0011] (3) Lamination: The CuCrZr alloys with different ECAP passes processed in step (2) were cut into thin slices of 150 mm × 12 mm × 1 mm. The surface was roughened with a steel brush and then degreased in acetone. The two copper alloys with different ECAP passes were then stacked, holes were punched at both ends, and fixed with aluminum pins.

[0012] (4) Rolling: The fixed double-layer copper alloy sheet obtained in step (3) is subjected to a one-time room temperature rolling deformation with a deformation amount of 50%. The roller speed during the rolling process is 16 r / min to ensure that the upper and lower layers of copper alloy can be combined after rolling.

[0013] (5) Annealing: The copper sheet rolled out in step (4) is placed in a resistance furnace for annealing to eliminate some internal stress, precipitate a nano-precipitate phase, stabilize the microstructure, and make the copper alloy layer bond more tightly and concretely. The annealing treatment is performed at a holding temperature of 200-500°C, preferably 400-500°C, and more preferably 400°C; and for a holding time of 0.5-1.5 hours, preferably 0.5-1 hour, and more preferably 0.05 hours.

[0014] (6) Accumulative rolling: Repeating steps (3) (4) (5) can produce a multilayer heterogeneous copper alloy with greater deformation, higher dislocation density and finer grains.

[0015] The present invention regulates the size of coarse and fine grains through ECAP and combines it with the cumulative rolling process to obtain a layered heterogeneous structure with alternating coarse and fine crystal layers. The grains in the fine crystal region are nanocrystalline, the grain size in the coarse crystal region is ≤45μm, and the grain size in the fine crystal region is ≤205nm.

[0016] The microstructure obtained by the present invention is distributed with nano-twins and Cr nano-precipitates. The nano-twin grain width is ≤50 nm, and the volume percentage is 7-10%. The nano-precipitates are ≤40 nm in size, and a small amount of micron-precipitates is also present. The total volume percentage of the Cr precipitates is 12-18%.

[0017] Compared with traditional strengthening processes, the preparation process of the present invention improves the shortcomings of single ECAP or cumulative rolling strengthening, which has limited effect and poor conductivity and plasticity, and effectively solves the contradiction between strength and conductivity of copper alloys. It is of great significance for the application of high-strength and high-conductivity copper alloys in integrated circuits, new energy and other fields.

[0018] Beneficial effects of the present invention:

[0019] 1. By combining the advantages of two severe plastic deformation methods, ECAP and cumulative rolling, the present invention produces a new nano-layered heterogeneous structure composed of dislocations, precipitates, and twins distributed within coarse and fine nanocrystalline layers. The large difference in hardness between the coarse and fine crystalline layers generates significant back stress, which can overcome the limitations of traditional fine grain strengthening and significantly enhance both the strength and plasticity of the material.

[0020] 2. The size of each layer of grains can be effectively controlled by different ECAP passes, and the required layered heterogeneous structure can be prepared by combining rolling.

[0021] 3. The presence of the coarse-grained layer in the alloy can reduce the scattering of electrons by grain boundaries and lattice distortion in the alloy, while ensuring the high strength of the alloy without significantly decreasing the conductivity. This meets the growing performance requirements of high-strength and high-conductivity copper alloys in industrial production and provides a new approach to balancing the contradictory relationship between the strength and conductivity of copper alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the present invention.

[0023] Figure 2 This is a schematic diagram of the layered heterogeneous microstructure of the CuCrZr alloy prepared by the present invention.

[0024] Figure 3 This is the phase diagram of the CuCrZr alloy gold coarse-grained layer obtained in Example 7.

[0025] Figure 4 This is a TEM photograph of the CuCrZr alloy fine grain layer obtained in Example 7. DETAILED DESCRIPTION

[0026] The present invention is further described below with reference to specific examples. The preparation process for a high-strength, high-conductivity layered heterogeneous copper alloy is as follows: solution treatment, equal-channel angular extrusion, lamination, rolling, annealing, and cumulative roll bonding. The experimental methods described in the examples are conventional unless otherwise noted. The reagents and materials described are commercially available unless otherwise noted. Example 1

[0027] (1) Solution treatment: The commercial CuCrZr alloy square material was placed in a resistance furnace for solution treatment. The specific process was to heat the furnace to 1000 °C and keep it at this temperature for 0.5 h at a heating rate of 5 °C / min. Then, it was quickly placed in a 5 wt.% NaCl solution to cool, and finally the black oxide layer on the surface of the alloy was polished off.

[0028] The composition of the CuCrZr alloy by mass ratio is Cr: 0.95-1.06%, Zr: 0.08-0.12%, trace amounts of impurities such as Fe, Zn, and P, and the balance is Cu.

[0029] (2) Equal angular extrusion: The alloy treated in step (1) was subjected to equal angular extrusion (ECAP) at room temperature for 0 and 2 passes, respectively, to obtain copper alloy bars with different grain sizes. The extrusion speed was 15 mm / min, the die had an inner angle of 110°, an outer angle of 0°, and an inner diameter of 12 mm × 12 mm.

[0030] (3) Lamination: The CuCrZr alloys of ECAP 0 and 2 passes processed in step (2) were cut into 150 mm × 12 mm × 1 mm thin slices, and the surface was roughened with a steel brush. Then, the slices were placed in acetone for degreasing. The two copper alloys of ECAP 0 and 2 passes were then stacked, holes were punched at both ends, and fixed with aluminum pins.

[0031] (4) Rolling: The fixed double-layer copper alloy sheet obtained in step (3) is subjected to a one-time room temperature rolling deformation to obtain a double-layer heterogeneous copper alloy. The rolling deformation is 50%, and the roller speed during the rolling process is 16 r / min.

[0032] (5) Annealing: The copper alloy rolled in step (4) is placed in a resistance furnace for annealing at a holding temperature of 200°C for 0.5 h.

[0033] The layered heterogeneous copper alloy prepared in this example had an average grain size of 31.5 μm in the coarse-grained layer (ECAP pass 0) and 178.3 nm in the fine-grained layer (ECAP pass 2), with volume fractions of 46.2% and 53.8%, respectively. Mechanical and electrical property testing revealed a tensile strength of 664 MPa in the rolling direction, an elongation of 18.7%, and an electrical conductivity of 78% IACS. Example 2

[0034] The difference between this embodiment and embodiment 1 is that the holding temperature of the annealing treatment in step (5) is 400°C and the holding time is 0.5h. Other operations are the same as those in embodiment 1.

[0035] The layered heterogeneous copper alloy prepared in this example had an average grain size of 38.3 μm in the coarse-grained layer (ECAP pass 0) and 188.5 nm in the fine-grained layer (ECAP pass 2), with volume fractions of 44.8% and 55.2%, respectively. Mechanical and electrical property testing revealed a tensile strength of 698 MPa in the rolling direction, an elongation of 21.3%, and an electrical conductivity of 88% IACS. Example 3

[0036] The difference between this embodiment and embodiment 1 is that the holding temperature of the annealing treatment in step (5) is 500° C. and the holding time is 0.5 h. Other operations are the same as those in embodiment 1.

[0037] The layered heterogeneous copper alloy prepared in this example had an average grain size of 42.1 μm and a volume fraction of 45.3% in the coarse-grained layer (ECAP pass 0), and an average grain size of 196.2 nm and a volume fraction of 54.7% in the fine-grained layer (ECAP pass 2). Mechanical and electrical property testing showed that the alloy had a tensile strength of 675 MPa in the rolling direction, an elongation of 22.7%, and an electrical conductivity of 87% IACS. Example 4

[0038] The difference between this embodiment and embodiment 1 is that the holding temperature of the annealing treatment in step (5) is 400°C and the holding time is 1 hour. Other operations are the same as those in embodiment 1.

[0039] The layered heterogeneous copper alloy prepared in this example has an average grain size of 45 μm (volume fraction 46.5%) in the coarse-grained layer (ECAP pass 0), an average grain size of 205.3 nm (volume fraction 54.5%) in the fine-grained layer (ECAP pass 2), an average grain size of 45 nm (volume fraction 7.6%) in the nanotwinned layer, and an average size of approximately 38.5 nm in the nanoprecipitated phase. Mechanical and electrical property testing revealed a tensile strength of 671 MPa in the rolling direction, an elongation of 28.5%, and an electrical conductivity of 89% IACS. Example 5

[0040] The difference between this embodiment and embodiment 1 is that the rolling deformation in step (4) is 65%, and the other operations are the same as embodiment 1.

[0041] The layered heterogeneous copper alloy prepared in this example had an average grain size of 30 μm and a volume fraction of 45.9% in the coarse-grained layer (ECAP pass 0), and an average grain size of 200.5 nm and a volume fraction of 54.1% in the fine-grained layer (ECAP pass 2). Mechanical and electrical property testing revealed a tensile strength of 683 MPa in the rolling direction, an elongation of 15.5%, and an electrical conductivity of 77% IACS. Example 6

[0042] (1) Solution treatment: same as in Example 1.

[0043] (2) Equal Angular Extrusion: The alloy treated in step (1) was subjected to equal angular extrusion (ECAP) at room temperature for 0 and 4 passes (only the number of ECAP passes was changed) to obtain copper alloy bars with different grain sizes. The extrusion speed was 15 mm / min, the die had an inner angle of 110°, an outer angle of 0°, and an inner diameter of 12 mm × 12 mm.

[0044] (3) Lamination: The CuCrZr alloys with ECAP passes 0 and 4, processed in step (2), were cut into 150 mm × 12 mm × 1 mm thin slices. The surfaces were roughened with a steel brush and then degreased in acetone. The two copper alloys with ECAP passes 0 and 4 were then stacked, holes were punched at both ends, and fixed with aluminum pins.

[0045] (4) Rolling: The fixed double-layer copper alloy sheet obtained in step (3) is subjected to a one-time room temperature rolling deformation to obtain a double-layer heterogeneous copper alloy. The rolling deformation is 50%, and the roller speed during the rolling process is 16 r / min.

[0046] (5) Annealing: The copper alloy rolled in step (4) is placed in a resistance furnace for annealing treatment at a holding temperature of 400°C for 0.5 h.

[0047] The layered heterogeneous copper alloy prepared in this example has an average grain size of 42.8 μm and a volume fraction of 45% in the coarse-grained layer (ECAP pass 0), and an average grain size of 135 nm and a volume fraction of 55% in the fine-grained layer (ECAP pass 4). Mechanical and electrical property testing revealed a tensile strength of 738 MPa in the rolling direction, an elongation of 24.1%, and an electrical conductivity of 82% IACS. Example 7

[0048] (1) Solution treatment: same as in Example 1.

[0049] (2) Equal Angular Extrusion: The alloy treated in step (1) was subjected to equal angular extrusion (ECAP) at room temperature for 2 or 4 passes (only the number of ECAP passes was changed) to obtain copper alloy bars with different grain sizes. The extrusion speed was 15 mm / min, the die had an inner angle of 110°, an outer angle of 0°, and an inner diameter of 12 mm × 12 mm.

[0050] (3) Lamination: The CuCrZr alloys processed in step (2) with 2 and 4 passes of ECAP were cut into 150 mm × 12 mm × 1 mm thin slices. The surfaces were roughened with a steel brush and then degreased in acetone. The two copper alloys with 2 and 4 passes of ECAP were then stacked, holes were punched at both ends, and fixed with aluminum pins.

[0051] (4) Rolling: The fixed double-layer copper alloy sheet obtained in step (3) is subjected to a one-time room temperature rolling deformation to obtain a double-layer heterogeneous copper alloy. The rolling deformation is 50%, and the roller speed during the rolling process is 16 r / min.

[0052] (5) Annealing: The copper alloy rolled in step (4) is placed in a resistance furnace for annealing treatment at a holding temperature of 400°C for 0.5 h.

[0053] The layered heterogeneous copper alloy prepared in this example had an average grain size of 209.8 nm in the coarse-grained layer (ECAP 2 passes) and 141.6 nm in the fine-grained layer (ECAP 4 passes), with volume fractions of 47% and 53%, respectively. Mechanical and electrical property testing revealed a tensile strength of 765 MPa in the rolling direction, an elongation of 23.8%, and an electrical conductivity of 74% IACS. Example 8

[0054] (1) Solution treatment: same as in Example 1.

[0055] (2) Equal angular extrusion: The alloy treated in step (1) was subjected to equal angular extrusion (ECAP) at room temperature for 0 and 4 passes (only the ECAP pass was changed) to obtain copper alloy bars with different grain sizes. The extrusion speed was 15 mm / min, the die had an inner angle of 110°, an outer angle of 0°, and an inner diameter of 12 mm × 12 mm.

[0056] (3) Lamination: The CuCrZr alloys with ECAP passes 0 and 4, processed in step (2), were cut into 150 mm × 12 mm × 1 mm thin slices. The surfaces were roughened with a steel brush and then degreased in acetone. The two copper alloys with ECAP passes 0 and 4 were then stacked, holes were punched at both ends, and fixed with aluminum pins.

[0057] (4) Rolling: The fixed double-layer copper alloy sheet obtained in step (3) is subjected to a one-time room temperature rolling deformation with a deformation amount of 50%. The roller speed during the rolling process is 16 r / min.

[0058] (5) Annealing: The copper alloy rolled in step (4) is placed in a resistance furnace for annealing treatment at a holding temperature of 400°C for 0.5 h.

[0059] (6) Accumulative rolling: The copper alloy annealed in step (5) is cut in the middle, and the coarse-grained layer surface and the fine-grained layer surface of the two copper alloy sheets are stacked up. Holes are punched at both ends and fixed with aluminum pins. Repeat steps (3) (4) (5) to obtain 4 layers of heterogeneous copper alloy.

[0060] The four-layer heterogeneous copper alloy prepared in this example had an average grain size of 22.3 μm and a volume fraction of 42.6% in the coarse-grained layer (ECAP pass 0), and an average grain size of 88.7 nm and a volume fraction of 57.4% in the fine-grained layer (ECAP pass 4). Mechanical and electrical property testing showed that the alloy had a tensile strength of 789 MPa in the rolling direction, an elongation of 21.9%, and an electrical conductivity of 81% IACS. Comparative Example 1

[0061] (1) Solution treatment: same as in Example 1.

[0062] (2) Equal angular extrusion: The alloy treated in step (1) was subjected to four equal angular extrusions (ECAP) at room temperature. The extrusion speed was 15 mm / min, the die had an inner angle of 110°, an outer angle of 0°, and an inner diameter of 12 mm × 12 mm.

[0063] (3) Rolling: The copper alloy after ECAP obtained in step (2) was subjected to room temperature rolling deformation, with a single rolling deformation of 10% and a total rolling deformation of 50%. The roller speed during the rolling process was 16 r / min.

[0064] (4) Annealing: The copper alloy rolled in step (3) is placed in a resistance furnace for annealing treatment at a holding temperature of 400°C for 0.5 h.

[0065] This comparative example demonstrates the preparation of a high-strength, high-conductivity copper alloy using a commonly used severe plastic deformation process. The copper alloy was directly rolled after ECAP treatment, without combining it with a cumulative roll-bonding process. The resulting alloy had an average grain size of 213.2 nm. Mechanical and electrical property testing revealed a tensile strength of 662 MPa in the rolling direction, an elongation of 15.3%, and a conductivity of 69% IACS. Compared to the ECAP + roll-bonding composite process used in the example, this alloy exhibited limited improvement in tensile strength, while exhibiting significantly reduced conductivity and plasticity. Comparative Example 2

[0066] (1) Solution treatment: same as in Example 1.

[0067] (2) Lamination: The CuCrZr alloy solution-treated in step (1) was cut into 150 mm × 12 mm × 1 mm thin slices, and the surface was roughened with a steel brush. Then, the slices were degreased in acetone. The two slices of copper alloy were then stacked, holes were punched at both ends, and the slices were fixed with aluminum pins.

[0068] (3) Rolling: The double-layer copper alloy fixed in step (2) is subjected to a one-time room temperature rolling deformation, with a total rolling deformation of 50%. The roller speed during the rolling process is 16 r / min.

[0069] (4) Annealing: The copper alloy rolled in step (3) is placed in a resistance furnace for annealing treatment at a holding temperature of 400°C for 0.5 h.

[0070] (5) Accumulative rolling: The copper alloy annealed in step (4) is cut in the middle and steps (2), (3) and (4) are repeated to obtain four layers of heterogeneous copper alloy.

[0071] This comparative example demonstrates a high-strength, high-conductivity copper alloy produced using a typical cumulative roll-bonding process. ECAP treatment was not performed before the roll-bonding process. After two roll-bonding cycles, the alloy exhibited an average grain size of 25.3 μm, with a small amount of nanotwins distributed throughout the microstructure. Mechanical and electrical property testing revealed a tensile strength of 689 MPa in the rolling direction, an elongation of 11.8%, and a conductivity of 67% IACS. Compared to the ECAP + roll-bonding composite process used in the example, the conductivity and ductility of this alloy were significantly reduced. Comparative Example 3

[0072] The difference between this example and Example 8 is that step (6) is cumulative rolling: the copper alloy annealed in step (5) is cut in the middle, the coarse grain layer surfaces of two copper alloy sheets are stacked on top of each other, holes are punched at both ends and fixed with aluminum pins, and steps (3) (4) (5) are repeated to obtain 4 layers of heterogeneous copper alloy.

[0073] The four-layer heterogeneous copper alloy prepared in this example had an average grain size of 24.1 μm and a volume fraction of 47.1% in the coarse-grained layer (ECAP pass 0), and an average grain size of 92.3 nm and a volume fraction of 52.9% in the fine-grained layer (ECAP pass 4). Mechanical and electrical property testing showed that the alloy had a tensile strength of 772 MPa in the rolling direction, an elongation of 19.4%, and an electrical conductivity of 84% IACS.

[0074] The room temperature tensile strength and electrical conductivity of the CuCrZr alloys prepared in all the above examples and comparative examples were tested, and the results are shown in Table 1.

[0075] Table 1 Mechanical and electrical properties of the embodiments and comparative examples .

[0076] Comparisons of the strength and conductivity of the above examples and comparative examples demonstrate that the layered heterogeneous CuCrZr alloy prepared using this method (ECAP-rolling composite process) achieves significantly greater tensile strength, while maintaining high electrical conductivity, compared to conventional ECAP+rolling deformation and cumulative rolling processes. Comparisons of Examples 1, 2, 3, and 4 demonstrate that, under the same process conditions, an annealing temperature of approximately 400°C for 0.5 hours achieves the optimal balance between strength and conductivity.

[0077] It can be seen from Comparative Example 2 and Examples 6 and 7 that the alloy combination of higher ECAP passes and lower ECAP passes is rolled, and the strength of the alloy obtained is significantly improved, but the conductivity is slightly lost. The copper alloy layer with a lower ECAP pass has a greater impact on the conductivity, and the conductivity of 0 pass is the best. It can be seen from Comparative Example 2 and Example 8 that increasing the rolling passes can significantly improve the strength of the alloy, breaking through the limit of copper alloy strength improvement, while the conductivity does not decrease significantly. The combination of copper plates with different ECAP passes and multiple cumulative rolling are the key to giving full play to the advantages of the ECAP-rolling process. It can be seen from Comparative Example 3 and Example 8 that the alternating distribution of coarse and fine nanocrystalline layers, compared with the bidirectional gradient distribution of the fine crystal layer outside the middle coarse crystal layer, can further improve the mechanical properties of the alloy without affecting its conductivity.

[0078] The above-described embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-described implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A high-strength and high-conductivity layered heterogeneous copper-chromium-zirconium alloy, characterized in that: The alloy structure is a nano-layered heterogeneous structure, including coarse and fine multi-layer nanocrystals and dispersed nano-twins and Cr nano-precipitated phases. The grain size of the coarse grain area is ≤45 μm, and the grain size of the fine grain area is ≤205 nm.

2. A method for preparing the high-strength and high-conductivity layered heterogeneous copper-chromium-zirconium alloy according to claim 1, characterized in that: The specific steps are as follows: (1) subjecting at least two CuCrZr alloys to solid solution treatment; (2) performing equal channel angular extrusion treatment on the CuCrZr alloy treated in step (1) in different passes; (3) Cutting the CuCrZr alloy obtained in step (2) into sheets, grinding and degreasing the surface to obtain a coarse-grained or fine-grained CuCrZr alloy sheet; stacking and fixing the coarse-grained CuCrZr alloy sheet and the fine-grained CuCrZr alloy sheet to obtain a double-layer alloy sheet; (4) The double-layer alloy sheet is subjected to one-time room temperature rolling deformation, with a deformation amount of 50% to 55%; (5) annealing the CuCrZr alloy subjected to the rolling deformation treatment in step (4) to obtain a layered heterogeneous copper-chromium-zirconium alloy; (6) Alternatively, the CuCrZr alloy annealed in step (5) is cut into the same sheet-like CuCrZr alloy, the surface of the coarse-grained layer and the surface of the fine-grained layer are superimposed and fixed, and steps (3), (4), and (5) are repeated to obtain the layered heterogeneous copper-chromium-zirconium alloy.

3. The method for preparing a high-strength and high-conductivity layered heterogeneous copper-chromium-zirconium alloy according to claim 2, characterized in that: The extrusion rate of the equal-diameter angular extrusion deformation in step (2) is 15 mm / min, the inner angle Φ of the die used is 110°, the outer angle Ψ is 0°, and the inner diameter is 12 mm×12 mm.

4. The method for preparing a high-strength and high-conductivity layered heterogeneous copper-chromium-zirconium alloy according to claim 2, wherein: The fixing method described in step (3) is to drill holes at both ends and use aluminum pins.

5. The method for preparing a high-strength and high-conductivity layered heterogeneous copper-chromium-zirconium alloy according to claim 2, characterized in that: The roller speed during the one-time room temperature rolling deformation process described in step (4) is 16 r / min.

6. The method for preparing a high-strength and high-conductivity layered heterogeneous copper-chromium-zirconium alloy according to claim 2, characterized in that: The specific parameters of the annealing treatment in step (5) are: holding temperature 200-500°C, holding time 0.5-1.5 h.

7. The method for preparing a high-strength and high-conductivity layered heterogeneous copper-chromium-zirconium alloy according to claim 2, characterized in that: The layered heterogeneous copper-chromium-zirconium alloy has a tensile strength of 664 MPa to 789 MPa and an electrical conductivity of 74% to 89% IACS.

8. The method for preparing a high-strength and high-conductivity layered heterogeneous copper-chromium-zirconium alloy according to claim 2, characterized in that: The copper-chromium-zirconium alloy described in step (1) has a composition of Cr: 0.8wt% to 1.2wt%, Zr: 0.05wt% to 0.15wt%, and the balance is copper.

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