High-dimensional-precision copper alloy profile and preparation method thereof

Abstract

The invention discloses a high-dimensional-precision copper alloy profile and a preparation method thereof. The method comprises the following steps: S1, setting a nickel and silicon feeding ratio according to a stoichiometric ratio so as to inhibit stray stress; s2, the micro lattice distortion state is locked through high-temperature solid solution and rapid quenching; s3, implementing two-stage stress regulation and control aging, and realizing stress field relaxation release by utilizing coupling of primary nuclear cluster precipitation and heating rate to form a semi-coherent dispersion strengthening phase and anchor dislocation; and S4, gradient path cooling is adopted to balance temperature difference stress, and secondary stress is eliminated. According to the method, whole-process stress regulation and control are implemented from a component source to gradient cooling, and the technical contradiction of stress accumulation in the hardening process of the profile is effectively solved. The residual stress of the obtained finished product profile is lower than 15 MPa, the dimensional change rate after heat preservation at 150 DEG C for 100 h is smaller than 0.005%, and the finished product profile has excellent stress relaxation resistance and dimensional stability.

Description

Technical Field

[0001] This invention relates to the field of copper alloy material processing technology, specifically to a high-precision copper alloy profile and its preparation method. Background Technology

[0002] Copper alloy profiles are widely used in electronic connectors, precision instruments, and semiconductor lead frames due to their excellent electrical and thermal conductivity and mechanical properties. With the increasing precision of industrial technology, the dimensional stability requirements for copper alloy profiles in related precision components are becoming increasingly stringent.

[0003] Traditional copper alloy manufacturing processes primarily focus on enhancing material strength through precipitation strengthening. However, during smelting, solution treatment, and hot deformation processing, copper alloys often accumulate significant residual stress. Due to the atomic radius differences between solute atoms such as nickel and silicon and the copper matrix, if the composition ratio fails to precisely match the stoichiometry of the precipitated phases, free atoms will remain in the copper alloy matrix, inducing microscopic lattice distortion. These unstable residual stresses are slowly released during subsequent precision machining or environmental temperature fluctuations, leading to slight deformation or warping of the profile. This deformation severely affects the precision assembly effect and long-term dimensional reliability of the product. Therefore, how to intervene in the internal stress of the profile throughout the entire process from the source of composition, microstructure evolution, and temperature stress control is a core technical challenge that urgently needs to be solved in the field of high-precision copper alloy manufacturing. Summary of the Invention

[0004] The technical problem this invention aims to solve is to provide a high-precision copper alloy profile and its preparation method. This invention achieves this by precisely controlling the mass ratio of nickel to silicon to match the target precipitated phase, and by combining solid solution energy-locking treatment and a two-stage stress-controlled aging process, systematically suppressing and eliminating multi-source residual stress throughout the entire preparation process. Ultimately, this invention enables the obtained copper alloy profile to construct a stable microstructure, thereby significantly improving the macroscopic dimensional stability of the copper alloy profile.

[0005] To achieve the above objectives, the present invention provides a method for preparing high-precision copper alloy profiles, comprising the following steps: S1. Elemental copper is melted to form a matrix molten pool, and nickel, silicon, aluminum and zirconium elements are added to the matrix molten pool; wherein, the mass ratio of nickel to silicon is set based on the stoichiometric ratio of the target nickel-silicon intermetallic compound, and the elements are fully fused by smelting the matrix molten pool to obtain a copper alloy liquid with uniform composition, so as to suppress stray stress caused by residual solute atoms in subsequent processes. S2. The copper alloy liquid is condensed and crystallized and hot-deformed to form a solid profile blank; then the solid profile blank is subjected to high-temperature solution treatment, and after the high-temperature solution treatment is completed, it is rapidly quenched so that the nickel, silicon, aluminum and zirconium elements form a supersaturated solid solution in the copper lattice and lock the microscopic lattice distortion state to obtain the profile to be aged. S3. The profile to be aged is held at a first temperature for a first duration to induce the nickel and silicon elements to precipitate high-density primary nuclei in the matrix of the profile to be aged; the profile to be aged is raised from the first temperature to a second temperature at a controlled heating rate and held for a second duration to induce the relaxation and release of the residual stress field inside the profile to be aged, and to guide the primary nuclei to evolve into a dispersed strengthening phase that is semi-coherent with the matrix of the profile to be aged, thereby obtaining the profile to be cooled; wherein, the second temperature is higher than the first temperature, and the first duration is longer than the second duration; S4. Control the profile to be cooled to the ambient temperature according to a controlled gradient path. By balancing the temperature difference stress distribution during the cooling process, the secondary stress generated inside the profile to be cooled is eliminated, and finally the finished copper alloy profile is obtained.

[0006] Preferably, in step S1, the mass ratio of nickel to silicon is 3.5:1 to 4.5:1.

[0007] Preferably, the amount of aluminum added is 0.05% to 0.3% by mass percentage, and the amount of zirconium added is 0.01% to 0.1%.

[0008] Preferably, in step S2, the temperature of the high-temperature solution treatment is 850℃~980℃, and the holding time is 1h~3h; the cooling rate of the rapid quenching is not less than 50℃ / s.

[0009] Preferably, in step S3, the first temperature is 350℃~450℃, the first duration is 4h~8h; the second temperature is 480℃~580℃, the second duration is 1h~3h; and the controlled heating rate is 3℃ / min~10℃ / min.

[0010] Preferably, in step S4, the controlled gradient path cooling includes: first cooling the profile to be cooled to 200℃~250℃ at a cooling rate of 5℃ / min~15℃ / min, holding it at that temperature for 0.5h~1h to make the core and surface temperatures of the profile to be cooled tend to be consistent, and then controlling the profile to be cooled to be slowly cooled to ambient temperature at a cooling rate of no more than 2℃ / min.

[0011] Preferably, in step S3, the controlled heating rate is nonlinearly adjusted based on the real-time volume fraction of the primary nuclei in the matrix of the profile to be aged; as the volume fraction of the primary nuclei increases, the heating rate is increased in stages, so as to use the micro compressive stress generated by the growth of the dispersed strengthening phase to offset the thermal tensile stress of the matrix of the profile to be aged, thereby achieving a dynamic balance of the micro-strain energy inside the profile to be aged.

[0012] Preferably, in step S3, after the primary nucleus cluster evolves into a dispersed strengthening phase, the mismatch between the dispersed strengthening phase and the matrix of the profile to be aged is controlled between 0.05% and 0.15%. The mismatch induces an elastic strain field in the matrix lattice of the profile to be aged, which anchors the dislocations inside the matrix of the profile to be aged, thereby improving the stress relaxation resistance of the finished copper alloy profile.

[0013] The present invention also provides a high-dimensional precision copper alloy profile, wherein the copper alloy profile is prepared by any of the above-described preparation methods.

[0014] Preferably, the copper alloy profile has a uniformly dispersed nickel-silicon precipitate phase in its matrix, and the volume fraction of the nickel-silicon precipitate phase in the matrix of the copper alloy profile is 3% to 8%; the residual stress value of the copper alloy profile is less than 15 MPa, and the dimensional change rate after being kept at 150°C for 100 h is less than 0.005%.

[0015] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention sets the feeding ratio of nickel and silicon elements based on the stoichiometry of the target nickel-silicon intermetallic compound, ensuring that solute atoms can be completely precipitated at a fixed ratio to the maximum extent during the aging stage. This design effectively reduces matrix lattice distortion caused by residual solute atoms, thereby enabling the method provided by this invention to suppress the formation of stray stress from the source, providing a stable microstructure prerequisite for achieving high dimensional accuracy in profiles.

[0016] Furthermore, the two-stage stress-controlled aging process employed in this invention fully utilizes the phased thermal activation effect. In the first temperature stage, the method provided by this invention induces the precipitation of high-density primary nuclei, thereby establishing a diffusely distributed nanoscale strengthening foundation. Subsequently, during the heating process to the second temperature, the thermal activation energy promotes the full relaxation and release of the residual stress field accumulated inside the profile in the previous process. This specific process sequence cleverly solves the technical contradiction that copper alloy profiles are prone to stress accumulation during the hardening process, enabling the resulting profile to achieve excellent strengthening effects while deeply eliminating its internal stress.

[0017] Furthermore, this invention establishes a complete end-to-end stress monitoring system through rapid quenching after solution treatment and gradient cooling after aging. In particular, the gradient cooling process used in step S4 balances the temperature gradient between the core and surface of the profile through a controlled cooling rate, thereby completely eliminating secondary stresses caused by temperature differences. Combined with the anchoring effect of the semi-coherent dislocations formed during the aging stage, the finished profiles produced by this invention exhibit extremely high resistance to stress relaxation and dimensional accuracy retention under complex service environments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow for a method of preparing a high-precision copper alloy profile provided by the present invention. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] In the preparation method described in this invention, the various process steps work synergistically to form a fully closed-loop control system for residual stress. (Reference) Figure 1 As shown, the present invention first performs matrix smelting through step S1. During the smelting process, technicians place elemental copper with a purity of not less than 99.9% into an induction melting furnace to melt and form a matrix molten pool. Based on the performance requirements of the target product, nickel, silicon, aluminum, and zirconium elements are precisely added to the matrix molten pool.

[0021] In the actual operation of step S1, the ratio of nickel to silicon is the key factor determining the dimensional stability of the final profile. This invention is based on a target nickel-silicon intermetallic compound (such as...). The stoichiometric ratio of nickel to silicon is set within the range of 3.5:1 to 4.5:1. This ratio design ensures that nickel and silicon atoms precipitate as completely as possible during subsequent aging, avoiding microscopic distortion stress caused by excess of one element remaining in the copper lattice. As an alternative, the elements are not limited to being elemental; they can also be added as copper-nickel master alloys or copper-silicon master alloys to further improve the uniformity of composition. Through thorough melting, the elements achieve atomic-level homogenization in the molten copper, thereby effectively suppressing stray stress caused by solute segregation.

[0022] The process then proceeds to the solution-locking energy stage shown in step S2. After the copper alloy liquid solidifies to form a billet, it is processed into a solid profile billet through hot deformation methods such as extrusion, drawing, or rolling. To eliminate work hardening and prepare for precipitation kinetics, the solid profile billet is subjected to solution treatment at a high temperature of 850°C to 980°C, with the holding time controlled between 1 hour and 3 hours. After the solution treatment, the invention performs rapid quenching at a rate of not less than 50°C / s. The physical significance of this step is to instantly lock the supersaturated solute atoms at high temperature into the copper lattice, forming a microscopic supersaturated solid solution. Although this energy-locking treatment temporarily preserves the microscopic lattice distortion, its highly consistent state creates a prerequisite for the unified stress release in the subsequent step S3.

[0023] In the two-stage stress-controlled aging process shown in step S3, this invention achieves a deep coupling between strengthening phase precipitation and stress release through segmented heat treatment. First, the profile to be aged is held at a first temperature of 350°C to 450°C for 4 to 8 hours. During this stage, high-density primary nuclei are induced in the matrix. Due to the relatively low first temperature, the growth rate of the nuclei is limited, which is conducive to the formation of a fine and diffuse microstructure distribution.

[0024] Furthermore, during the transition from the first temperature to the second temperature, the present invention employs a controlled heating rate of 3°C / min to 10°C / min. In a preferred embodiment of the present invention, the controlled heating rate is nonlinearly adjusted based on the real-time volume fraction of the primary nuclei in the matrix. As the proportion of precipitates increases, the present invention progressively increases the heating rate, utilizing the micro-compressive stress generated on the surrounding matrix during the growth of the precipitates to dynamically offset the thermal tensile stress generated in the matrix due to the heating, thereby ensuring that the micro-strain energy within the profile remains in dynamic equilibrium. When the temperature is raised to the second temperature of 480°C to 580°C, a short holding time of 1 to 3 hours is performed, at which point the residual stress field undergoes sufficient relaxation and release, and the nuclei evolve into a dispersed strengthening phase that is semi-coherent with the matrix. By controlling the misfit degree between 0.05% and 0.15%, these strengthening phases can lock dislocations like "anchors," significantly improving the stress relaxation resistance of the profile.

[0025] Finally, in the gradient cooling stage of step S4, this invention specifically controls the secondary stress that is easily generated in the profile. The profile to be cooled is first cooled to 200°C to 250°C at a rate of 5°C / min to 15°C / min and then held at that temperature for 0.5h to 1h. This pause allows the thermal fields of the core and surface of the profile to converge. Subsequently, the profile is cooled to room temperature very slowly at a rate not exceeding 2°C / min. Compared to conventional direct air cooling or water cooling methods, this gradient cooling path avoids secondary thermal stress caused by excessive internal and external temperature differences, ensuring that the residual stress value of the finished copper alloy profile is below 15MPa.

[0026] To further verify the technical effects of the present invention, several specific embodiments and comparative examples are listed below for illustration. Example

[0027] This embodiment uses the following parameters: by mass percentage, the amount of nickel added is 4.0%, the amount of silicon added is 1.0% (at this time, the mass ratio of nickel to silicon is 4.0:1); the amount of aluminum added is 0.15%, the amount of zirconium added is 0.05%, and the balance is copper and unavoidable impurities. In step S2, the high-temperature solution temperature set in this embodiment is 920℃, and the holding time is 2h. In step S3, the first temperature is set to 400℃, and the holding time is 6h; then the temperature is increased to the second temperature of 530℃ at a heating rate of 5℃ / min, and the holding time is 1.5h. In step S4, the gradient cooling path is to first reduce the temperature to 220℃ at a rate of 10℃ / min, hold for 1h, and then slowly cool to the ambient temperature at a rate of 1.5℃ / min. The residual stress of the finished copper alloy profile obtained in Example 1 was 10.5 MPa, and the dimensional change rate after holding at 150°C for 100 h was only 0.002%. Example

[0028] The amount of nickel added is 3.15%, and the amount of silicon added is 0.9% (at this time, the mass ratio of nickel to silicon is 3.5:1); the amount of aluminum added is 0.05%, and the amount of zirconium added is 0.01%, with the remainder being copper and unavoidable impurities. In step S2, the high-temperature solution temperature set in this embodiment is 850℃, and the holding time is 3h. In step S3, the first temperature is set to 350℃, and the holding time is 8h; then the temperature is increased to the second temperature of 480℃ at a heating rate of 3℃ / min, and the holding time is 3h. In step S4, the gradient cooling path is to first reduce the temperature to 200℃ at a rate of 5℃ / min, hold for 1h, and then slowly cool to the ambient temperature at a rate of 1.0℃ / min. Testing showed that the finished copper alloy profile obtained in Example 2 also had excellent performance, with a residual stress value of 12.8 MPa, and all indicators demonstrated extremely high dimensional stability.

[0029] Comparative Example 1 The composition was the same as in Example 1, but only a single-stage aging process at 530°C was used in step S3, and air cooling was applied directly after step S4. Testing showed that the residual stress of the profile obtained in Comparative Example 1 was as high as 48 MPa, and the dimensional change rate at 150°C reached 0.015%. Therefore, without the two-stage stress control and gradient cooling process described in this invention, the profile could not achieve the expected dimensional stability.

[0030] In summary, this invention successfully resolves the technical contradiction of internal stress accumulation during the hardening process of copper alloy profiles through end-to-end stress management, from smelting proportions to gradient cooling. The above description is merely a preferred embodiment of this invention. For those skilled in the art, various improvements and modifications can be made without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a high-precision copper alloy profile, characterized in that, Includes the following steps: S1. Elemental copper is melted to form a matrix molten pool, and nickel, silicon, aluminum and zirconium elements are added to the matrix molten pool; wherein, the mass ratio of nickel to silicon is set based on the stoichiometric ratio of the target nickel-silicon intermetallic compound, and the elements are fully fused by smelting the matrix molten pool to obtain a copper alloy liquid with uniform composition, so as to suppress stray stress caused by residual solute atoms in subsequent processes. S2. The copper alloy liquid is condensed and crystallized and hot-deformed to form a solid profile blank; then the solid profile blank is subjected to high-temperature solution treatment, and after the high-temperature solution treatment is completed, it is rapidly quenched so that the nickel, silicon, aluminum and zirconium elements form a supersaturated solid solution in the copper lattice and lock the microscopic lattice distortion state to obtain the profile to be aged. S3. The profile to be aged is held at a first temperature for a first duration to induce the nickel and silicon elements to precipitate high-density primary nuclei in the matrix of the profile to be aged; the profile to be aged is raised from the first temperature to a second temperature at a controlled heating rate and held for a second duration to induce the relaxation and release of the residual stress field inside the profile to be aged, and to guide the primary nuclei to evolve into a dispersed strengthening phase that is semi-coherent with the matrix of the profile to be aged, thereby obtaining the profile to be cooled; wherein, the second temperature is higher than the first temperature, and the first duration is longer than the second duration; S4. Control the profile to be cooled to the ambient temperature according to a controlled gradient path. By balancing the temperature difference stress distribution during the cooling process, the secondary stress generated inside the profile to be cooled is eliminated, and finally the finished copper alloy profile is obtained.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of nickel to silicon is 3.5:1 to 4.5:

1.

3. The preparation method according to claim 1, characterized in that, The amount of aluminum added is 0.05% to 0.3% by mass percentage, and the amount of zirconium added is 0.01% to 0.1%.

4. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the high-temperature solution treatment is 850℃~980℃, and the holding time is 1h~3h; the cooling rate of the rapid quenching is not less than 50℃ / s.

5. The preparation method according to claim 1, characterized in that, In step S3, the first temperature is 350℃~450℃, and the first duration is 4h~8h; the second temperature is 480℃~580℃, and the second duration is 1h~3h; the controlled heating rate is 3℃ / min~10℃ / min.

6. The preparation method according to claim 1, characterized in that, In step S4, the controlled gradient path cooling includes: first cooling the profile to be cooled to 200℃~250℃ at a cooling rate of 5℃ / min~15℃ / min, holding it at that temperature for 0.5h~1h to make the core and surface temperatures of the profile to be cooled tend to be consistent, and then controlling the profile to be cooled to be slowly cooled to ambient temperature at a cooling rate of no more than 2℃ / min.

7. The preparation method according to claim 1, characterized in that, In step S3, the controlled heating rate is nonlinearly adjusted based on the real-time volume fraction of the primary nuclei in the matrix of the profile to be aged; as the volume fraction of the primary nuclei increases, the heating rate is increased in stages to utilize the micro compressive stress generated by the growth of the dispersed strengthening phase to offset the thermal tensile stress in the matrix of the profile to be aged, thereby achieving a dynamic balance of the micro-strain energy inside the profile to be aged.

8. The preparation method according to claim 1, characterized in that, In step S3, after the primary nucleus cluster evolves into a dispersed strengthening phase, the mismatch between the dispersed strengthening phase and the matrix of the profile to be aged is controlled between 0.05% and 0.15%. The mismatch induces an elastic strain field in the matrix lattice of the profile to be aged, which is used to anchor the dislocations inside the matrix of the profile to be aged, thereby improving the stress relaxation resistance of the finished copper alloy profile.

9. A high-precision copper alloy profile, characterized in that, The copper alloy profile is prepared by any one of claims 1 to 8.

10. The copper alloy profile according to claim 9, characterized in that, The copper alloy profile has a uniformly dispersed nickel-silicon precipitate phase in its matrix, and the volume fraction of the nickel-silicon precipitate phase in the matrix of the copper alloy profile is 3% to 8%; the residual stress value of the copper alloy profile is less than 15 MPa, and the dimensional change rate after being kept at 150°C for 100 h is less than 0.005%.

Images