Method for simultaneously improving strength and plasticity of copper alloy

Abstract

The invention discloses a method for simultaneously improving the strength and plasticity of a copper alloy, and belongs to the technical field of material preparation. According to the method, germanium is added into the copper alloy, the mass percent of germanium in the copper alloy is 9%, and the copper-germanium alloy with the strength and the plasticity improved at the same time is obtained through rotary swaging treatment, annealing treatment, pre-twisting treatment and short-time annealing treatment. The copper-germanium alloy is subjected to pre-twisting and then short-time annealing treatment, so that a composite heterostructure material combining double peaks and gradients from the surface to the core is obtained, and the copper-germanium alloy with the double heterostructures is obtained, the yield strength of the copper-germanium alloy is more than two times that of the annealed copper-germanium alloy, and the plasticity of the copper-germanium alloy is basically kept unchanged.

Description

Technical Field

[0001] The invention relates to a method for simultaneously improving the strength and plasticity of a copper alloy, and belongs to the technical field of material preparation. Background Art

[0002] With the development of industries such as aerospace and automobile, the demand for high-strength and high-ductility materials has become more urgent. Traditional copper alloys have a mismatch between strength and plasticity. They have good plasticity but low strength. At present, traditional large plastic deformation preparation methods such as cumulative tying and equal channel angular extrusion sacrifice plasticity to a certain extent to improve strength, but cannot achieve a balance between strength and plasticity.

[0003] Therefore, there is an urgent need to provide a method for simultaneously improving the strength and plasticity of copper alloys. Summary of the invention

[0004] In order to simultaneously improve the strength and plasticity of a copper alloy, the present invention provides a method for simultaneously improving the strength and plasticity of a copper alloy. The method comprises: adding germanium to a copper alloy so that the mass percentage of germanium in the copper alloy is 9%, and obtaining a copper-germanium alloy having both improved strength and plasticity through rotary forging, annealing, pre-twisting and short-time annealing.

[0005] Preferably, after rotary forging, a copper-germanium alloy with a diameter of 7 mm is obtained.

[0006] Preferably, the annealing treatment conditions are: annealing treatment is performed at 700° C.-800° C. for 100-120 min.

[0007] Preferably, the rate of the pre-twisting treatment is 60° / min-90° / min, and the total twisting degree is 270°.

[0008] Preferably, the short-time annealing treatment condition is: annealing at 550° C. for 5 minutes.

[0009] Beneficial Effects of the Invention

[0010] (1) The present invention performs a pre-twisting and short-time annealing treatment on a copper-germanium alloy. The present invention firstly finds that a short treatment time forms a double-peak structure on the surface and the grain size gradually increases from the surface to the core, thereby obtaining a copper alloy with a double-peak grain and gradient double heterogeneous structure.

[0011] (2) During the tensile test, the mechanical properties of the copper alloy are improved due to the synergy between the double-peak hard and soft areas on the surface, the fine grains on the surface and the coarse grains in the core, and the combined effect of multiple deformation mechanisms. The yield strength is increased by 2 times while maintaining good plasticity. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1The tensile curves of Example 1, Comparative Examples 1 to 4 and annealed copper-germanium alloy at room temperature are compared.

[0013] Figure 2 This is a hardness diagram from the surface to the core of the copper alloy subjected to pre-twisting and short-time annealing in Example 1.

[0014] Figure 3 This is a metallographic image from the surface to the core of the copper alloy subjected to pre-twisting and short-time annealing treatment in Example 1. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0016] Example 1

[0017] A method for simultaneously improving the strength and plasticity of a copper alloy comprises the following steps:

[0018] (1) Germanium is added to a copper alloy for smelting to obtain a copper-germanium alloy with a germanium mass percentage of 9%.

[0019] (2) The copper alloy is subjected to rotary forging to obtain a copper-germanium alloy rod with a diameter of 7 mm.

[0020] (3) Annealing the copper-germanium alloy rod obtained in step (2) at 700° C. for 2 hours.

[0021] (4) The copper-germanium alloy rod treated in step (3) is subjected to a pre-twisting treatment, with a twisting speed of 60° / min, and twisting 270° requires 4.5 min.

[0022] (5) The copper-germanium alloy rod treated in step (4) is short-term annealed at 550° C. for 5 min. Figure 2 As shown, a gradient structure with increasing hardness from the surface to the core is obtained, and a double-peak structure of the grains is obtained (such as Figure 3 ). A heterostructured copper-germanium alloy with improved strength and ductility is obtained.

[0023] In this embodiment, the yield strength and ultimate tensile strength of the copper alloy with double grain peaks and gradient double heterogeneous structure prepared by pre-twisting 270° and short-time annealing at 550°C are improved while maintaining good plasticity.

[0024] Comparative Example 1

[0025] For comparison, the difference between this comparative example and implementation 1 is that the short-time annealing temperature is 500° C., and the specific steps are:

[0026] (1) Germanium is added to a copper alloy for smelting to obtain a copper-germanium alloy with a germanium mass percentage of 9%.

[0027] (2) The copper alloy is subjected to rotary forging to obtain a copper-germanium alloy rod with a diameter of 7 mm.

[0028] (3) Annealing the copper-germanium alloy rod obtained in step (2) at 700° C. for 2 hours.

[0029] (4) The copper-germanium alloy rod treated in step (3) is subjected to a pre-twisting treatment, with a twisting speed of 60° / min, and twisting 270° requires 4.5 min.

[0030] (5) The copper-germanium alloy rod treated in step (4) is short-term annealed at 500° C. for 5 min to obtain a copper-germanium alloy.

[0031] The copper alloy with a grain gradient dual heterogeneous structure prepared in this embodiment has a higher yield strength and ultimate tensile strength, but its plasticity is also reduced.

[0032] Comparative Example 2

[0033] In contrast, the difference between this comparative example and Example 1 is that the short-time annealing temperature is 12 min, and specifically comprises the following steps:

[0034] (1) Germanium is added to a copper alloy for smelting to obtain a copper-germanium alloy with a germanium mass percentage of 9%.

[0035] (2) The copper alloy is subjected to rotary forging to obtain a copper-germanium alloy rod with a diameter of 7 mm.

[0036] (3) Annealing the copper-germanium alloy rod obtained in step (2) at 700° C. for 2 hours.

[0037] (4) The copper-germanium alloy rod treated in step (3) is subjected to a pre-twisting treatment, with a twisting speed of 60° / min, and twisting 270° requires 4.5 min.

[0038] (5) The copper-germanium alloy rod treated in step (4) is short-term annealed at 550° C. for 12 min to obtain a copper-germanium alloy with improved strength and plasticity.

[0039] The homogeneous structure copper-germanium alloy obtained in this comparative example has lower yield strength and ultimate tensile strength, but higher plasticity.

[0040] Comparative Example 3

[0041] In contrast, this comparative example is different from Example 1 in that short-time annealing is not performed, and specifically comprises the following steps:

[0042] (1) Germanium is added to a copper alloy for smelting to obtain a copper-germanium alloy with a germanium mass percentage of 9%.

[0043] (2) The copper alloy is subjected to rotary forging to obtain a copper-germanium alloy rod with a diameter of 7 mm.

[0044] (3) Annealing the copper-germanium alloy rod obtained in step (2) at 700° C. for 2 hours.

[0045] (4) The copper-germanium alloy rod treated in step (3) is subjected to a pre-twisting treatment at a twisting speed of 60° / min. It takes 4.5 min to twist 270° to obtain the copper-germanium alloy.

[0046] The gradient structure heterostructure copper-germanium alloy obtained in this comparative example has higher yield strength and ultimate tensile strength, but its plasticity is reduced.

[0047] Comparative Example 4

[0048] As a comparison, the difference between this comparative example and Example 1 is that the pre-twist is 180°, which specifically includes the following steps:

[0049] (1) Germanium is added to a copper alloy for smelting to obtain a copper-germanium alloy with a germanium mass percentage of 9%.

[0050] (2) The copper alloy is subjected to rotary forging to obtain a copper-germanium alloy rod with a diameter of 7 mm.

[0051] (3) Annealing the copper-germanium alloy rod obtained in step (2) at 700° C. for 2 hours.

[0052] (4) The copper-germanium alloy rod treated in step (3) is subjected to a pre-twisting treatment, with a twisting speed of 60° / min, and twisting 180° requires 3 minutes.

[0053] (5) The copper-germanium alloy rod treated in step (4) is short-term annealed at 550° C. for 5 min to obtain a copper-germanium alloy.

[0054] The gradient structure heterostructure copper-germanium alloy prepared in this comparative example has higher yield strength and ultimate tensile strength, but its plasticity is also reduced.

[0055] Comparison of tensile curves of the copper-germanium alloys prepared in Example 1 and Comparative Examples 1 to 4 and the annealed copper-germanium alloys (annealed copper-germanium alloys refer to alloy materials obtained by annealing in step (2) only) at room temperature. Figure 1 As shown, from Figure 1It can be seen that in Example 1, the yield strength and ultimate tensile strength of the copper alloy with double grain peaks and gradient double heterogeneous structure prepared by pre-twisting 270° and short-time annealing at 550°C are improved, while maintaining good plasticity; its yield strength and ultimate tensile strength reach 298MPa and 492MPa respectively, and the uniform elongation reaches 41%; although the copper alloy obtained in Comparative Example 1 has higher yield strength and ultimate tensile strength, its plasticity is also reduced, and its yield strength and ultimate tensile strength reach 418MPa and 534MPa respectively, and the uniform elongation reaches 20%, because the crystallization temperature of the copper-germanium alloy has not been reached, the internal grains have not yet crystallized, and the degree of dislocation density occurring in the recovery is small; the homogeneous structure copper-germanium alloy obtained in Comparative Example 2 has lower yield strength and ultimate tensile strength, but its plasticity is higher, its yield strength and ultimate tensile strength are 175MPa and 448MPa respectively, and the uniform elongation is 46%. This is because its annealing time is long, the internal grain crystallization rate is high, and the dislocation density is reduced, resulting in a serious decrease in its strength; the gradient structure heterostructure copper-germanium alloy obtained in comparative example 3 has a higher yield strength and ultimate tensile strength, but its plasticity is reduced, its yield strength and ultimate tensile strength are 440MPa and 543MPa respectively, and the uniform elongation is 14%; the gradient structure heterostructure copper-germanium alloy prepared in comparative example 4 has a higher yield strength and ultimate tensile strength, but its plasticity is also reduced, its yield strength and ultimate tensile strength are 360MPa and 513MPa respectively, and the uniform elongation is 23%; Figure 1 It can also be seen that a dual heterostructure copper-germanium alloy was obtained, whose yield strength is more than twice that of the annealed copper-germanium alloy and whose plasticity remains basically unchanged.

[0056] By comparison, it can be seen that the copper-germanium alloy is subjected to a pre-twisting 270° and short-time annealing treatment at 550℃ to form a double-peak structure and its grain size gradually increases from the surface to the core, resulting in a copper alloy with double-peak surface grains and gradient double heterogeneous structure. During the tensile test of the mechanical test, the mutual synergy between the double-peak surface hard zone and the soft zone, the surface fine grains and the core coarse grains, and the combined action of multiple deformation mechanisms improve the mechanical properties of the copper alloy, and the yield strength is increased by 2 times while maintaining good plasticity.

Claims

1. A method for simultaneously improving the strength and plasticity of a copper alloy, characterized in that: Germanium element is added to the copper alloy so that the mass percentage of germanium in the copper alloy is 9%, and a copper-germanium alloy with improved strength and plasticity is obtained through rotary forging, annealing, pre-twisting and short-time annealing.

2. The method for simultaneously improving the strength and plasticity of a copper alloy according to claim 1, characterized in that: The annealing conditions are: annealing at 700°C-800°C for 100-120 minutes.

3. The method for simultaneously improving the strength and plasticity of a copper alloy according to claim 1, characterized in that: The rate of the pre-twisting treatment is 60° / min-90° / min, and the total twisting degree is 270°.

4. The method for simultaneously improving the strength and plasticity of a copper alloy according to claim 1, characterized in that: The short-time annealing treatment conditions are: annealing at 550° C. for 5 minutes.

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