Method for improving strength and plasticity of middle-high layer staggered energy metal material

Abstract

The invention discloses a method for improving the strength and plasticity of a middle-high layer staggered energy metal material, and belongs to the technical field of metal material preparation and processing. According to the method, N times of deep cooling online treatment (N is larger than or equal to 2) are carried out on the middle-high layer staggered energy metal material, a deep cooling medium is liquid nitrogen or liquid helium, plastic deformation is achieved by means of continuous rolling and other processes, and online aging heat treatment can be carried out between the treatment chambers. After treatment, the material forms a nano twin crystal structure, so that the strength and plasticity are synergistically improved, and the high conductivity is kept. According to the method, the limitation of a traditional strengthening technology is broken through, dislocation motion and stress distribution are regulated and controlled through the nano twin boundaries, fracture is avoided, and the conductivity is guaranteed. Meanwhile, the technology can be operated in an integrated and continuous mode, is suitable for large-scale production of wires and thin strips, is high in machining efficiency and stable in performance batch, and meets the requirements for metal materials of high-end connectors in the fields of integrated circuits, new energy automobiles and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material preparation and processing, and specifically, it is a method for improving the strength and plasticity of medium and high stacking fault energy metal materials. Background Art

[0002] With the rapid development of the fields of integrated circuits, new energy vehicles, and low-altitude aircraft, these industries have put forward extremely stringent requirements for the comprehensive performance of high-end connectors in electrical systems. Under complex working conditions of high voltage, large current, mechanical vibration, and thermal cycling, high-end connectors not only need to have high strength to withstand mechanical stress and maintain structural stability, but also need to have high plasticity to avoid brittle fracture during deformation. At the same time, high electrical conductivity is also a key indicator to ensure its electrical performance.

[0003] However, traditional metal strengthening technologies are in a dilemma when dealing with these requirements. For example, dislocation strengthening and precipitation strengthening can significantly improve the strength of metal materials, but they will sacrifice plasticity, resulting in brittle fracture of the materials when stressed; while annealing treatment can improve the plasticity of the materials, but inevitably causes a significant decrease in strength. This contradiction between strength and plasticity has become the core bottleneck restricting the performance breakthrough of high-end connectors.

[0004] The emergence of nano-twin structures provides a new idea for coordinating the strength-plasticity contradiction of metal materials. It can improve the strength of materials by hindering the dislocation movement perpendicular to the twin boundaries, while allowing the dislocation slip parallel to the twin boundaries, thus retaining a certain amount of plasticity. However, there are limitations in the application of this technology at present. Mainstream materials of connectors, such as medium and high stacking fault energy metals like aluminum, pure copper, CuCrZr, etc., are difficult to form nano-twin structures through conventional processing methods due to their own deformation mechanism limitations. Although existing laboratory technologies can introduce a small amount of nano-twins into these materials through means such as impact or cryogenic treatment, these methods have problems such as uncontrollable processes, limited sample sizes, and poor repeatability, and cannot meet the requirements of large-scale industrial production. Summary of the Invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a method for improving the strength and plasticity of medium and high stacking fault energy metal materials, which synergistically improves the strength and plasticity of the materials on the basis of ensuring the electrical conductivity of the metal materials through N times of cryogenic in-situ deformation.

[0006] To achieve the above object, the specific solution adopted by the present invention is as follows: A method for improving the strength and plasticity of medium and high stacking fault energy metal materials, which performs N times of cryogenic in-situ treatment on the medium and high stacking fault energy metal materials, and the cryogenic in-situ treatment is to place the metal materials in a cryogenic medium and simultaneously apply plastic deformation; After N times of cryogenic in - line treatment, the microstructure of the metal material has a nano - twin structure. The nano - twin structure restricts dislocation movement through the twin - boundary strengthening effect to improve strength, and at the same time maintains strain coordination through the dislocation - coordinated deformation mechanism, thereby achieving a synergistic improvement of strength and plasticity; N≥2.

[0007] Furthermore, the cryogenic medium is liquid nitrogen or liquid helium, and plastic deformation is achieved through continuous rolling, drawing or spinning processes.

[0008] Furthermore, between the M - th cryogenic in - line treatment and the (M + 1)-th cryogenic in - line treatment, an in - line aging heat treatment step is also included, where 1≤M≤N - 1.

[0009] Furthermore, the specific method of the in - line aging heat treatment is: removing the metal material that has undergone the M - th cryogenic in - line treatment from the cryogenic medium and performing annealing treatment at a preset temperature to regulate the dislocation density and twin stability.

[0010] Furthermore, the stacking fault energy of the metal material is higher than 55 mJ / m 2 .

[0011] Furthermore, the shape of the metal material is any one of plate - shaped, strip - shaped, and filament - shaped.

[0012] Beneficial effects: (1) Comprehensive performance breakthrough: Under the action of continuous cryogenic in - line temperature - field dynamic regulation, a nano - twin structure is formed inside the medium - high stacking - fault - energy metal material. This nano - twin structure has multi - scale interfaces, and through the synergistic effect between the interfaces, the synchronous improvement of strength and plasticity is achieved. In traditional strengthening technologies, the improvement of strength is often accompanied by the reduction of plasticity, while the present invention breaks through this physical limit. During the process of improving strength and plasticity, this method can maintain the high conductivity of the material, meeting the requirements of high - end connectors in terms of electrical performance.

[0013] (2) Defect regulation advantage: The present invention effectively introduces a nano - twin structure to construct a dislocation storage network and a stress - release channel. The nano - twin boundary, as an obstacle barrier to dislocation movement, can restrict dislocation slip, thereby improving the strength of the material. For example, when the material is subjected to an external force, dislocations are blocked when they encounter the nano - twin boundary during movement, enabling the material to withstand a greater external force without deformation, thus improving the strength of the material. On the other hand, dislocations parallel to the twin boundary have a high degree of slip freedom. When local stress concentration occurs in the material, these dislocations can relieve stress through slip, preventing the material from fracture failure. In addition, compared with ordinary large - angle grain boundaries, the electron scattering effect caused by the nano - twin interface is extremely low, which ensures the original conductivity of the material, so that while the strength and plasticity of the material are improved, its application in the electrical field is not affected.

[0014] (3)Industrial adaptability: By integrating cryogenic treatment and traditional thermomechanical treatment processes online, the present invention realizes the continuous and controllable introduction of nanotwin structures. This process can well adapt to the large-scale production of wire rods and thin strips. Compared with the laboratory impact / low-temperature deformation process, the processing efficiency is greatly improved. Moreover, the batch stability of the material properties prepared by this process is good, which can meet the strict requirements for the consistency of material properties during the mass production of high-end connectors. For example, in actual production, cryogenic online treatment and aging heat treatment can be continuously carried out on metal materials, and each batch of materials can ensure similar strength, plasticity, and electrical conductivity, providing a reliable material guarantee for the large-scale production of high-end connectors. Description of the Drawings

[0015] Figure 1 Microstructure diagram of the product obtained in Example 1. Detailed Embodiments

[0016] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] The present invention discloses a method for improving the strength and plasticity of medium-high stacking fault energy metal materials. This method is applicable to metal materials with a stacking fault energy higher than 55 mJ / m². Specifically: the medium-high stacking fault energy metal material is subjected to N times of cryogenic online treatment. Cryogenic online treatment refers to synchronously applying plastic deformation to the metal material while placing it in a cryogenic medium. After N times of cryogenic online treatment, nanotwin structures will be formed in the microstructure of the metal material. This nanotwin structure restricts dislocation movement through the twin boundary strengthening effect, thereby improving the material strength; at the same time, the strain coordination is maintained by means of the dislocation coordinated deformation mechanism, realizing the coordinated improvement of strength and plasticity. Among them, N≥2.

[0018] Specifically, the cryogenic medium is selected from liquid nitrogen or liquid helium, and the plastic deformation can be realized by continuous rolling, drawing or spinning processes.

[0019] It should be noted that an online aging heat treatment step is set between the Mth cryogenic online treatment and the (M + 1)th cryogenic online treatment (1≤M≤N - 1). The specific operation of the online aging heat treatment is to take out the metal material that has undergone the Mth cryogenic online treatment from the cryogenic medium and perform annealing treatment at a preset temperature to control the dislocation density and twin stability.

[0020] The present invention focuses on the innovation of the continuous processing technology for medium and high stacking fault energy metal materials, breaks through the technical boundaries of traditional thermomechanical treatment, realizes the controllable introduction of nano-twin structures through continuous cryogenic (liquid nitrogen / helium temperature range) on-line treatment, and synergistically optimizes strength and plasticity while ensuring electrical conductivity, providing key material support for the mass production of high-reliability connectors.

[0021] This method is applicable to the processing and forming of metal wire rods, wire materials, sheet and strip materials, especially suitable for the continuous and mass production of strip materials and extremely fine wire materials with large cumulative deformation amounts, to meet the urgent needs of metal materials and products for high-end connectors in fields such as integrated circuits, new energy vehicles, and low-altitude aircraft.

[0022] Example 1 This example relates to a method for continuous cryogenic on-line treatment of CuCrZr sheets for automotive connectors. The total number of cryogenic on-line treatment levels for the CuCrZr sheets is 2 levels, and the total number of aging heat treatment levels is 2 levels. The specific steps are as follows: (1) Primary cryogenic on-line treatment: Immerse the CuCrZr sheet in liquid nitrogen for cryogenic treatment, and perform continuous deformation treatment (rolling treatment), which is divided into 8 passes in total, and the total deformation amount reaches 85%; during this process, the cryogenic liquid nitrogen environment and plastic deformation act synchronously, promoting the change of the internal structure of the material and laying the foundation for the formation of subsequent nano-twin structures; (2) Primary aging heat treatment: Directly perform on-line annealing on the CuCrZr sheet after the primary cryogenic on-line treatment. The annealing temperature is set at 400 °C, and the holding time is 120 minutes; through this step, the dislocation density and twin stability inside the material are regulated, making the microstructure of the material more stable and preparing for subsequent processing and performance improvement; (3) Secondary cryogenic on-line treatment: Immerse the CuCrZr sheet after the primary aging heat treatment in liquid nitrogen again for on-line deformation treatment (rolling treatment), which is divided into 6 passes, and the total deformation amount is increased to 95%; this step further promotes the formation and development of nano-twin structures, and further improves the strength and plasticity of the material; (4) Secondary aging heat treatment: Perform on-line annealing on the material after the secondary cryogenic on-line treatment. The annealing temperature is 350 °C, and the holding time is 120 minutes; through this annealing treatment, the internal structure of the material is further optimized, and the nano-twin structure is stabilized, finally obtaining CuCrZr sheets with excellent performance.

[0023] The microstructure of the CuCrZr sheet obtained in this example is as Figure 1 shown, and it can be clearly seen from the figure that nano-twin structures are introduced into the material microstructure.

[0024] Example 2 This embodiment relates to a continuous cryogenic on-line treatment method for C7075 aluminum alloy strips. There are 2 levels of cryogenic on-line treatment and 2 levels of aging heat treatment for aluminum alloy plates. The specific steps are as follows: (1)Primary cryogenic on-line treatment: Immerse the aluminum alloy plate in cryogenic liquid nitrogen and perform continuous deformation treatment (rolling treatment), which is divided into 5 passes in total, and the total deformation amount reaches 70%; (2)Primary aging heat treatment: Directly perform on-line annealing on the aluminum alloy plate that has undergone primary cryogenic on-line treatment. The annealing temperature is set at 110 °C, and the holding time is 80 minutes; (3)Secondary cryogenic on-line treatment: Immerse the aluminum alloy plate after primary aging heat treatment in cryogenic liquid nitrogen again and perform on-line deformation treatment (rolling treatment), which is divided into 4 passes, and the total deformation amount is increased to 85%; (4)Secondary aging heat treatment: Perform on-line annealing on the material after secondary cryogenic on-line treatment. The annealing temperature is 120 °C, and the holding time is 90 minutes.

[0025] Example 3 This embodiment relates to a continuous cryogenic on-line treatment method for Cu-5Fe alloy wires. There are 2 levels of cryogenic on-line treatment and 2 levels of aging heat treatment for Cu-5Fe alloy. The specific steps are as follows: (1)Primary cryogenic on-line treatment: Immerse the Cu-5Fe alloy in cryogenic liquid nitrogen and perform continuous deformation treatment (drawing treatment), which is divided into 6 passes in total, and the total deformation amount reaches 70%; (2)Primary aging heat treatment: Directly perform on-line annealing on the Cu-5Fe alloy that has undergone primary cryogenic on-line treatment. The annealing temperature is set at 500 °C, and the holding time is 70 minutes; (3)Secondary cryogenic on-line treatment: Immerse the Cu-5Fe alloy after primary aging heat treatment in cryogenic liquid nitrogen again and perform on-line deformation treatment (drawing treatment), which is divided into 4 passes, and the total deformation amount is increased to 92%; (4)Secondary aging heat treatment: Perform on-line annealing on the material after secondary cryogenic on-line treatment. The annealing temperature is 500 °C, and the holding time is 90 minutes.

[0026] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that normal temperature deformation is used in both step (1) and step (3).

[0027] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that normal temperature deformation is used in both step (1) and step (3).

[0028] Comparative Example 3 The difference between Comparative Example 3 and Example 3 is that normal temperature deformation is used in both step (1) and step (3).

[0029] The performance tests were carried out on the products obtained in Examples 1-3 and Comparative Examples 1-3, and the results are shown in Table 1.

[0030] Table 1 Performance test results of the products obtained in Examples 1-2 and Comparative Example 1 As can be seen from Table 1, compared with Comparative Example 1, the product obtained in Example 1 has significantly improved strength while maintaining high conductivity, and the elongation rate has more than doubled. Compared with Comparative Example 2, the product obtained in Example 2 has significantly improved strength while maintaining high conductivity, and the elongation rate has also increased. Compared with Comparative Example 3, the product obtained in Example 3 has significantly improved strength while maintaining high conductivity, and the elongation rate has also increased. This fully demonstrates the remarkable effect of the cryogenic on-line treatment method of the present invention in improving the strength and plasticity of medium-high stacking fault energy metal materials, and can fully meet the requirements of metal materials for high-end connectors in fields such as new energy vehicles and low-altitude aircraft.

[0031] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Any equivalent transformation or modification made according to the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for improving the strength and plasticity of medium stacking fault energy metal materials, characterized in that Perform N times of cryogenic in-line treatment on medium and high stacking fault energy metal materials. The cryogenic in-line treatment is to place the metal materials in a cryogenic medium and apply plastic deformation synchronously. After N times of cryogenic in-line treatment, the metal materials have a nano-twin structure in their microstructure. The nano-twin structure restricts dislocation movement through the twin boundary strengthening effect to improve strength, and at the same time maintains strain coordination through the dislocation coordinated deformation mechanism, so as to achieve the simultaneous improvement of strength and plasticity; N≥2.

2. The method for improving the strength and plasticity of a medium-high stacking fault energy metal material according to claim 1, wherein The cryogenic medium is liquid nitrogen or liquid helium, and the plastic deformation is realized through continuous rolling, drawing or spinning processes.

3. A method for improving the strength and plasticity of medium and high stacking fault energy metal materials according to claim 1, characterized in that, An in-line aging heat treatment step is also included between the Mth cryogenic in-line treatment and the (M + 1)th cryogenic in-line treatment, where 1≤M≤N - 1.

4. A method for improving the strength and plasticity of medium stacking fault energy metal materials according to claim 3, characterized in that, The specific method of the in-line aging heat treatment is: remove the metal materials that have undergone the Mth cryogenic in-line treatment from the cryogenic medium, and perform annealing treatment at a preset temperature to control the dislocation density and twin stability.

5. A method for improving the strength and plasticity of medium stacking fault energy metal materials according to claim 1, characterized in that, The stacking fault energy of the metal material is higher than 55 mJ / m 2 .

6. A method for improving the strength and plasticity of medium stacking fault energy metallic materials according to claim 1, characterized in that The shape of the metal materials is any one of plate-shaped, strip-shaped, and filament-shaped.

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