Preparation method of high-strength and high-conductivity copper-chromium-zirconium alloy

Abstract

The application discloses a preparation method of high-strength and high-conductivity copper-chromium-zirconium alloy and belongs to the field of non-ferrous metal material processing. In view of the problem that the strength and conductivity of the traditional Cu-Cr-Zr alloy are difficult to be improved simultaneously, the application adopts a process route combining solid solution treatment, aging pretreatment, liquid nitrogen temperature zone rolling and low-temperature annealing. The aging pretreatment makes the nano Cr-rich phase disperse and precipitate, purifies the matrix and improves the subsequent work hardening capacity; the liquid nitrogen rolling suppresses dynamic recovery, introduces high dislocation density and nano deformation twin; and the low-temperature annealing promotes the further precipitation of residual solute and simultaneously retains the twin and fine-grain structure. The Cu-Cr-Zr alloy prepared by the method has a hardness of 163 HV and a conductivity of 77 % IACS, realizes the simultaneous improvement of the strength and conductivity, and is suitable for high-demand application fields such as high-speed railway contact lines and lead frame.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal material processing, specifically relating to a method for preparing a high-strength, high-conductivity copper-chromium-zirconium alloy by combining aging treatment, liquid nitrogen temperature rolling, and low-temperature annealing. Background Technology

[0002] Copper-chromium-zirconium alloys (Cu-Cr-Zr) are widely used in applications requiring high conductivity and mechanical properties, such as high-speed railway contact wires, integrated circuit lead frames, and resistance welding electrodes, due to their excellent electrical and thermal conductivity and moderate strength. Traditional strengthening methods include solution strengthening, precipitation strengthening through aging, and cold working. However, simple solution treatment combined with aging has limited precipitation strengthening effect, and the strength is insufficient for high-end applications; while room-temperature large deformation rolling can improve strength, it introduces a large number of dislocations and vacancies, leading to a sharp drop in electrical conductivity; although low-temperature rolling (such as liquid nitrogen rolling) can suppress dynamic recovery, it is still difficult to achieve an excellent strength-conductivity match if not properly combined with aging processes. Therefore, how to achieve a synergistic improvement in strength and electrical conductivity through process combinations while ensuring process stability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing high-strength and high-conductivity copper-chromium-zirconium alloy. By using a synergistic process path of solution treatment, aging treatment, liquid nitrogen temperature rolling, and low-temperature annealing, the method solves the problem that it is difficult to synergistically improve the strength and conductivity of alloys in the prior art.

[0004] The technical solution of the invention includes the following steps:

[0005] (1) Solution treatment: Cu-Cr-Zr alloy is subjected to solution treatment at a temperature of 900–980℃ for 2–6 hours, followed by water quenching to room temperature to obtain a supersaturated solid solution;

[0006] (2) Aging treatment: The alloy after solid solution is subjected to aging treatment at a temperature of 400–500℃ and held for 2–8 hours. Then it is cooled in the furnace or air-cooled. The above aging treatment precipitates nano-Cr-rich phase and purifies the copper matrix.

[0007] (3) Liquid nitrogen temperature zone rolling: After aging treatment, the alloy is immersed in liquid nitrogen and cooled to -196°C. The alloy is subjected to multi-pass rolling deformation. Between each pass, it is re-immersed in liquid nitrogen and cooled to -196°C to keep the alloy in the liquid nitrogen temperature zone during rolling, suppress dynamic recovery, and introduce high dislocation density and nano-deformation twins.

[0008] (4) Low-temperature annealing: The alloy rolled by liquid nitrogen is annealed at 350–450℃ to promote further precipitation of residual solutes while retaining twin and fine-grained structures.

[0009] Preferably, the Cu-Cr-Zr alloy contains 0.5–1.5 wt.% Cr, 0.02–0.2 wt.% Zr, and the balance is Cu.

[0010] Preferably, in step (3), the reduction in each rolling pass during liquid nitrogen temperature rolling is 5%–10%, and the total rolling deformation is 50%–95%.

[0011] Preferably, in step (4), the low-temperature annealing process is held at a temperature of 0.5–2 hours, followed by furnace cooling or air cooling.

[0012] The optimal process parameters are as follows: the solution treatment temperature in step (1) is 950℃ and the holding time is 4 h; the aging treatment temperature in step (2) is 450℃ and the holding time is 4 h; the total rolling deformation in the liquid nitrogen temperature zone in step (3) is 93.75%; and the low temperature annealing temperature in step (4) is 400℃ and the holding time is 1 h.

[0013] The beneficial effects of this invention are:

[0014] 1. Synergistic improvement of strength and electrical conductivity: Through a combination of aging treatment, liquid nitrogen rolling and low temperature annealing, an excellent match of hardness ≥160 HV and electrical conductivity ≥75% IACS was obtained. In the example, it reached 163 HV and 77% IACS.

[0015] 2. Unique microstructure: The alloy contains high-density dislocations and nanoscale deformed twins, while the Cr precipitates are uniformly distributed in spherical and rod-shaped forms, grain boundary migration is suppressed, and recrystallized grains are fine.

[0016] 3. Good process stability: Applicable to typical Cu-Cr-Zr alloys such as commercial C18150, requiring no special equipment and easy to promote industrialization. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention;

[0018] Figure 2 The curves showing the change in hardness of alloys in Example 1, Comparative Examples 1 and 2 as a function of rolling deformation are shown.

[0019] Figure 3 The curves show the change in electrical conductivity of alloys in Example 1, Comparative Examples 1 and 2 before annealing as a function of rolling deformation.

[0020] Figure 4 Electrical conductivity variation curves of samples subjected to solution treatment-aging-liquid nitrogen rolling (total deformation 93.75%) at different annealing temperatures;

[0021] Figure 5Here are SEM tissue images and EDS elemental distribution maps of the sample from Example 1;

[0022] Figure 6 The image shows the XRD pattern of the sample from Example 1. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0024] Example 1 (solution treatment - aging - liquid nitrogen rolling - annealing)

[0025] Commercial C18150 alloy (Cr 1.0 wt.%, Zr 0.1 wt.%, Cu balance) was used. The alloy was heated to 950℃ and held for 4 h for solution treatment, followed by water quenching to room temperature to obtain a supersaturated solid solution. Subsequently, the solution-treated alloy was aged at 450℃ for 4 h and furnace cooled to room temperature to allow Cr, Zr, and other elements to precipitate in nanoscale Cr-rich phases. The aged alloy was then immersed in liquid nitrogen and cooled to -196℃. Immediately after removal, it was subjected to multi-pass rolling with a reduction of 5% per pass and a total deformation of 93.75%. The alloy was re-immersed in liquid nitrogen for cooling between each pass. Finally, the liquid nitrogen-rolled alloy was annealed at 400℃ for 1 h and furnace cooled to room temperature.

[0026] Performance test results: Hardness 163 HV, conductivity 77% IACS. Figure 5 As shown, microscopic characterization (SEM / EDS) revealed a large number of diffusely distributed spherical and rod-shaped Cr-enriched phases, with no coarse precipitates or obvious recrystallized grains.

[0027] Comparative Example 1 (Solution-Room Temperature Rolling-Annealing)

[0028] In contrast, this embodiment uses the same method as in Example 1, except that the alloy is solution treated (950°C, 4 h), quenched in water to room temperature and then directly rolled at room temperature (5% reduction per pass, 93.75% total deformation), and then annealed (400°C, 1 h).

[0029] Performance test results: Hardness 110 HV, Electrical conductivity 70% IACS. This comparison shows that without aging treatment, both the strengthening effect and electrical conductivity are poor.

[0030] Comparative Example 2 (solution treatment - aging - room temperature rolling - annealing)

[0031] In contrast, this embodiment uses the same method as in Example 1, except that the alloy is solution treated (950°C, 4 h) and quenched to room temperature before aging (450°C, 4 h), then rolled at room temperature (5% reduction per pass, 93.75% total deformation), and then annealed (400°C, 1 h).

[0032] Performance test results: Hardness 160 HV, electrical conductivity 72% IACS. This comparison shows that although room temperature rolling can achieve higher hardness, the electrical conductivity is about 5 percentage points lower than that of liquid nitrogen rolling in Example 1.

[0033] Comparative Example 3 (solution treatment - liquid nitrogen rolling - annealing)

[0034] In contrast, this embodiment uses the same method as in Example 1, except that the alloy is solution treated (950°C, 4 h) and quenched in water to room temperature before being directly rolled in liquid nitrogen (5% reduction per pass, 93.75% total deformation), and then annealed (400°C, 1 h).

[0035] Performance test results: Hardness 140 HV, electrical conductivity 68% IACS. This comparison shows that even with liquid nitrogen rolling, the electrical conductivity is still significantly lower than that of Example 1 without aging treatment.

[0036] Comparative Example 4 (solution-aging-liquid nitrogen rolling)

[0037] In contrast, this embodiment uses the same method as Example 1, except that the alloy is solution treated (950℃ / 4h) and quenched in water to room temperature before aging (450℃ / 4h), and then rolled in liquid nitrogen (93.75%) without annealing.

[0038] Performance test results: Hardness approximately 190 HV, electrical conductivity approximately 52% IACS.

[0039] This indicates that although liquid nitrogen rolling can achieve the highest hardness, it results in extremely low electrical conductivity, and annealing is necessary to restore its conductivity.

[0040] To further verify the effect of different annealing temperatures on conductivity, this invention performed annealing treatment at the specified annealing temperature after solution treatment-aging-liquid nitrogen rolling (5% reduction per pass, total deformation 93.75%). The test results are as follows: Figure 4 As shown, the electrical conductivity of the product gradually recovers as the annealing temperature increases.

[0041] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 3, aging treatment is a key step in achieving high hardness and high electrical conductivity. As can be seen from the comparison between Example 1 and Comparative Example 4, low-temperature annealing is crucial for restoring electrical conductivity after liquid nitrogen rolling. As can be seen from the comparison between Example 1 and Comparative Example 2, using liquid nitrogen rolling while simultaneously employing low-temperature annealing, compared to room-temperature rolling, can increase electrical conductivity by approximately 5 percentage points while maintaining high hardness. Therefore, it can be seen that these three processes work synergistically to achieve a combined improvement in strength and conductivity; omitting any one step will lead to a significant reduction in a certain property.

Claims

1. A method for preparing a high-strength, high-conductivity copper-chromium-zirconium alloy, characterized in that, The steps are as follows: (1) Solution treatment: Cu-Cr-Zr alloy is subjected to solution treatment at a temperature of 900–980℃ for 2–6 hours, followed by water quenching to room temperature to obtain a supersaturated solid solution; (2) Aging pretreatment: The alloy after solution treatment is aged at a temperature of 400–500℃ and held for 2–8 hours. Then it is cooled in the furnace or air-cooled. The above aging treatment precipitates nano-Cr-rich phase and purifies the copper matrix. (3) Liquid nitrogen temperature zone rolling: After aging treatment, the alloy is immersed in liquid nitrogen and cooled to -196°C. The alloy is subjected to multi-pass rolling deformation. Between each pass, it is re-immersed in liquid nitrogen and cooled to -196°C to keep the alloy in the liquid nitrogen temperature zone during rolling, suppress dynamic recovery, and introduce high dislocation density and nano-deformation twins. (4) Low-temperature annealing: The alloy rolled by liquid nitrogen is annealed at 350–450℃ to promote further precipitation of residual solutes while retaining twin and fine-grained structures.

2. The method for preparing high-strength, high-conductivity copper-chromium-zirconium alloy according to claim 1, characterized in that, The Cu-Cr-Zr alloy contains 0.5–1.5 wt.% Cr, 0.02–0.2 wt.% Zr, and the balance is Cu.

3. The method for preparing high-strength, high-conductivity copper-chromium-zirconium alloy according to claim 1, characterized in that, In step (3), the reduction in each pass of the liquid nitrogen temperature zone rolling is 5%–10%, and the total rolling deformation is 50%–95%.

4. The method for preparing high-strength, high-conductivity copper-chromium-zirconium alloy according to claim 3, characterized in that, In step (4), the low-temperature annealing process involves holding the temperature for 0.5–2 hours, followed by furnace cooling or air cooling.

5. The method for preparing a high-strength, high-conductivity copper-chromium-zirconium alloy according to claim 4, characterized in that, The solution treatment temperature in step (1) is 950℃ and the holding time is 4 h; the aging pretreatment temperature in step (2) is 450℃ and the holding time is 4 h; the total rolling deformation in the liquid nitrogen temperature zone in step (3) is 93.75%; the low temperature annealing temperature in step (4) is 400℃ and the holding time is 1 h.

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