A high-strength high-conductivity copper alloy material and a preparation method thereof

Abstract

The application discloses a high-strength and high-conductivity copper alloy material and a preparation method thereof. The copper alloy material adds elements such as Cr, Hf, P, Ce, Zn and Ag into copper according to the precipitation characteristics of the precipitation strengthening type copper alloy, controls the precipitation phase of the alloy, realizes the strengthening of the matrix by two kinds of nanometer strengthening phases, and improves the mechanical properties, electrical properties and softening resistance of the alloy. After traditional solid solution treatment, pre-aging treatment, pre-cooling deformation treatment and regression treatment are added, the grains of the alloy can be effectively refined, the precipitation sequence of the multiple nanometer strengthening phases can be controlled, and the strengthening effect of the precipitation strengthening phase is as much as possible retained. The high-strength and high-conductivity copper alloy material is obtained by combining the combined deformation heat treatment, and has excellent mechanical properties (more than 700 MPa) and electrical properties (more than 70% IACS).

Description

Technical Field

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

[0002] Copper alloys, as functional structural materials with high strength, excellent electrical and thermal conductivity, and good wear and corrosion resistance, are widely used in energy and power, electronics and electrical appliances, transportation, marine engineering, and other fields. With the rapid development of high-tech industries such as 5G electronic communications, new energy vehicles, very large-scale integrated circuits, and high-speed rail transit, the demand for copper alloys, especially those with high strength, high conductivity, and specialized properties, is increasing. Furthermore, higher requirements are being placed on the comprehensive performance of copper alloy materials. While ensuring the combined properties of high strength and high conductivity, they must also exhibit excellent softening resistance and be able to operate in harsh, high-temperature environments.

[0003] Traditional high-strength and high-conductivity copper alloys often improve their mechanical properties at the expense of some electrical conductivity. Although introducing a large number of elements into copper alloys can strengthen the matrix through solid solution strengthening, the solid solution elements will greatly destroy the periodic potential field of the metal crystal, significantly reducing the electrical conductivity of the alloy. The synergistic addition of elements that can precipitate as simple substances or intermetallic compounds, and the use of combined deformation-aging and other thermomechanical treatment methods can promote the dissolution of the added elements from the matrix in the form of strengthening phases, which can purify the matrix to a certain extent and achieve a simultaneous increase in electrical conductivity and mechanical properties. However, this method has its upper limit. It is limited by the solid solubility, and the purification and strengthening effects that can be achieved cannot be endlessly improved.

[0004] The Cu-Zn, Cu-Mg, and Cu-Zr alloys developed in the early stages of high-strength and high-conductivity copper alloy development relied primarily on solid solution strengthening, resulting in unsatisfactory strength and conductivity. While the more widely used precipitation-strengthened Cu-Fe-P, Cu-Ni-Si, and Cu-Cr alloys have achieved generational improvements in overall performance, they also have certain drawbacks and each has its own performance limits. Although the high mass percentage of Si added to Cu-Ni-Si alloys provides sufficient precipitation momentum for Ni2Si, the residual Si atoms in the copper matrix severely deteriorate the alloy's electrical conductivity, making it difficult for the conductivity to exceed 50% IACS. The Fe element in Cu-Fe-P alloys has a limited strengthening effect on the alloy. When added in small amounts, the conductivity can reach 90% IACS, but the strength is only 450 MPa. Increasing the Fe addition can improve the strength at the expense of some conductivity, but this often outweighs the benefits. The tensile strength is difficult to exceed 600 MPa, and the conductivity also drops below 80% IACS. The precipitated Cr phase in Cu-Cr alloys will significantly coarsen with the extension of aging time and the increase of aging temperature, greatly reducing its contribution to the mechanical properties of the alloy and making it difficult for the tensile strength to exceed 630 MPa.

[0005] Although the tensile strength of Cu-Fe-P and Cu-Cr alloys can be improved through extreme deformation conditions (such as cryogenic deformation and severe plastic deformation), reaching levels difficult to achieve with conventional deformation methods, thereby achieving excellent overall performance, the performance improvements brought about by extreme deformation conditions are achieved at the expense of the possibility of industrial large-scale production. How to simultaneously achieve high strength and high conductivity to obtain high-performance copper alloys with excellent comprehensive properties has always been a hot topic and difficulty in research, and is also a symbol of the technological level of the high-performance copper processing industry. This forces us to develop new high-performance copper alloy systems to meet the high-performance demands of modern industry and high-tech industries. Summary of the Invention

[0006] To address the shortcomings of the prior art, the first objective of the present invention is to provide a high-strength, high-conductivity copper alloy material. The copper alloy material provided by the present invention utilizes a different strengthening strategy from conventional high-strength, high-conductivity copper alloys. By regulating the types and amounts of alloying elements, the material increases the types of the alloy's primary nanoscale strengthening phases while ensuring the substantial precipitation of the added elements. This significantly improves the alloy's mechanical properties while maintaining a stable electrical conductivity, resulting in an alloy exhibiting excellent overall performance.

[0007] The second object of the present invention is to provide a method for preparing a high-strength and high-conductivity copper alloy material. Compared with conventional traditional preparation methods, the preparation method provided by the present invention is simple and controllable while improving the comprehensive performance of the alloy, adapting to the specific conditions of industrial production, and suitable for industrial-scale production. Through the preparation method of the present invention, it is possible to prepare an alloy with finer grains, enhance the contribution of the fine grain strengthening mechanism to the mechanical properties of the alloy, and at the same time, provide sufficient precipitation power to promote the precipitation of the precipitate phase on a large scale, so that the alloy can obtain more excellent comprehensive performance. The improvement in comprehensive performance is not selective due to the compositional differences of the precipitation-strengthened high-strength and high-conductivity copper alloy, and has a universal strengthening effect. In addition, the preparation method provided by the present invention has an additional organizational regulation effect on the multi-nanoscale strengthening phase copper alloy material provided by the present invention, and can regulate the precipitation order of the precipitate phase.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a high-strength and high-conductivity copper alloy material. The copper alloy material is composed of the following components by mass percentage: 0.4-1.5wt% of Cr, 0.6-1.5wt% of Hf, 0-0.02wt% of P, 0-0.15wt% of Ce, 0-0.2wt% of Zn, 0-0.2wt% of Ag, and the balance being Cu.

[0010] The copper alloy material provided by the present invention is a CuCrHf alloy material, and Cr and Hf in the CuCrHf alloy are both major added elements, which are the source of the superiority of the high-strength and high-conductivity copper alloy material of the present invention over conventional copper alloys. The composition design of traditional high-strength and high-conductivity copper alloys is based on a certain nano-strengthening phase as the core, and other elements are selected with the strengthening idea of ​​promoting precipitation or modifying the precipitated phase. For example, taking the copper alloy material containing Hf as an example, due to the limited limit solid solubility of the Hf element in the Cu matrix, the current mainstream use of the Hf element is as a solid solution strengthening element in other alloy systems, with a small amount of addition and limited strengthening effect on the alloy.

[0011] The simultaneous addition of high Cr and Hf contents to the CuCrHf alloy provided by the present invention increases the types of high-density nanoscale strengthening phases (Cr and CuHf phases) in the alloy, and has greater precipitation potential and strength improvement than traditional high-strength and high-conductivity copper alloys with a single nanoscale precipitate phase as the strengthening phase (Fe phase in Cu-Fe-P alloy, Ni2Si phase in Cu-Ni-Si alloy, and Cr phase in Cu-Cr alloy). It should be pointed out that although the addition amounts of Cr and Hf are relatively high, the electrical conductivity of the CuCrHf alloy will not be unable to achieve a significant increase like the Cu-Ni-Si alloy. This is because the room temperature solid solubility of Cr and Hf in copper is close to zero. After the combined thermomechanical treatment, the Cr and Hf elements can be fully desolvated from the matrix in the form of precipitated phases, ensuring that the alloy has a high electrical conductivity. The addition of Hf element also has the effect of reducing the stacking fault energy of the alloy, so that the alloy forms deformation twins during conventional cold rolling deformation, hinders the interaction between dislocations, retains a higher dislocation density and more substructures in the alloy matrix, increases the recrystallization temperature and softening resistance of the alloy, and effectively improves the work hardening rate and final mechanical properties of the alloy.

[0012] In addition, the present invention also adds trace additive elements P, Ce, Zn, and Ag. On the one hand, they can control the smelting quality or refine the grains. For example, the P element can purify the matrix, improve the fluidity of the copper alloy melt, and enhance the casting quality of the ingot; the Ce element can refine the grains; trace amounts of Ag and Zn elements have little effect on the electrical conductivity of the alloy, and can achieve solid solution strengthening of the matrix with a slight loss of electrical conductivity. On the other hand, these trace elements can effectively regulate the morphology of the precipitated phase, so that the CuHf phase and the Cr phase can be dispersed in the matrix in a spherical phase, thereby improving the comprehensive performance of the alloy.

[0013] With the cooperation of the above components and contents, the alloy of the present invention has excellent comprehensive properties, such as high hardness, high strength, high electrical conductivity and high softening resistance temperature.

[0014] The element content of the alloy of the present invention should be controlled within the scope of the present invention to produce an effective synergistic effect. If the Cr element is too little, it cannot provide sufficient precipitation kinetics, making it difficult to achieve sufficient strengthening and matrix purification effects, resulting in a sharp decline in various performance indicators of the final alloy product. Excessive Cr elements will cause the formation of coarse Cr-rich primary phases in the matrix. These Cr phases increase in number and size as the degree of excess increases, but their effect on improving the strength of the material is very limited, and they are also not conducive to subsequent preparation and processing technology and grain refinement. If the Hf element is too little, it also cannot provide sufficient precipitation kinetics. Although the added Hf element can play a certain role in solid solution strengthening in the matrix, the slight increase in strength is far less than the decrease in conductivity compared to the aggravated electron scattering effect it brings. Excessive Hf elements will also increase the number and size of coarse Hf-rich primary phases in the matrix. In severe cases, the excess may even produce CuHf amorphous, which is detrimental to the overall performance of the material. P, Ce, Ag, and Zn are trace elements in the high-strength, high-conductivity copper alloy provided by the present invention. They can improve smelting quality or control the alloy's microstructure, significantly impacting the alloy's overall performance. However, excessive addition is not recommended. Excessive P, Ce, and Zn content, in particular, can dramatically reduce the alloy's electrical conductivity, failing to significantly strengthen it and instead worsening its overall performance. Excessive additions can negate this effect. When controlled within the present invention's range, element additions can have minimal impact on electrical conductivity or be extracted from the matrix, thereby avoiding solid solution in the Cu matrix and increasing electron scattering by the lattice.

[0015] In a preferred embodiment, the copper alloy material is composed of the following components by mass percentage: Cr 0.4-0.7wt.%, Hf 0.6-0.9wt.%, P 0-0.02wt.%, Ce 0-0.02wt.%, Zn 0-0.02wt.%, Ag 0-0.2wt.%, and the balance is Cu.

[0016] Further preferably, the copper alloy material is composed as follows by mass percentage: the copper alloy material is composed as follows by mass percentage: Cr 0.7wt.%, Hf 0.9wt.%, P 0.02wt.%, Ce 0.01wt.%, Zn 0.01wt.%, Ag 0.02wt.%, and the balance is Cu.

[0017] In a preferred embodiment, in the high-strength and high-conductivity copper alloy material, there is interaction between multiple nanoscale precipitated phases and dislocations, which are pinned and entangled with each other and dispersed in the matrix. The grain size of the high-strength and high-conductivity copper alloy material is ≤30μm, and twins are contained in the grains.

[0018] The high-strength and high-conductivity copper alloy material provided by the present invention has fine grains and a large number of twins. There is an interaction between the high-density multiple nanoscale precipitates and the high-density dislocations, which pin and entangle each other. This shows that the nanoscale precipitates can effectively pin the migration of dislocations, thereby improving the strength and toughness of the alloy.

[0019] The present invention also provides a method for preparing a high-strength and high-conductivity copper alloy material. First, the raw materials are mixed according to the designed composition ratio, smelted to obtain an alloy liquid, and the alloy liquid is cast into a copper alloy ingot. The copper alloy ingot is then subjected to homogenization annealing treatment, thermal deformation treatment, and solid solution treatment in sequence to obtain a solid solution alloy material. Finally, the solid solution alloy material is subjected to pre-aging treatment, pre-cold deformation treatment, regression treatment, and combined deformation heat treatment in sequence to obtain a high-strength and high-conductivity copper alloy material.

[0020] The preparation method of the present invention first uses a medium frequency melting furnace to carry out smelting under an atmospheric atmosphere, and casts the molten metal into shape to complete the preparation of the copper alloy ingot. Then the copper alloy ingot is subjected to conventional organizational control, including: homogenization annealing treatment, thermal deformation treatment, and solid solution treatment. After completing these treatments, most of the defects of the casting are eliminated, and the elements added within the scope of the present invention are all solid-dissolved into the matrix of the copper alloy. The purpose of the homogenization annealing treatment is to eliminate the segregation inside the casting grains during the smelting and casting process as much as possible. The thermal deformation treatment is to further eliminate the casting defects of the casting, and the solid solution treatment can effectively form a solid solution of trace elements with the copper matrix. Finally, the alloy that has completed the solid solution is subjected to pre-aging treatment, pre-cold deformation treatment, regression treatment and combined deformation heat treatment to prepare an alloy sample with excellent performance. The processing process of the alloy is the core of this preparation method. The precipitation-strengthening phase produced during the aging stage enhances the dislocation strengthening effect produced during the cold deformation process, allowing rapid and extensive recovery recrystallization during the regression stage. This results in a pre-aged sample with finer grains, which can then be subjected to conventional combined thermomechanical treatment. This combined thermomechanical treatment, which includes multiple passes of cold rolling and aging, promotes the precipitation of alloying elements dissolved in the crystal lattice, intensifying the proliferation of dislocations during deformation and increasing the values ​​of precipitation strengthening and deformation strengthening.

[0021] In the present invention, it is crucial to perform pre-aging treatment, pre-cold deformation treatment, and regression treatment before the combined thermomechanical treatment. If the alloy material after the solution treatment is directly subjected to the combined deformation treatment, although a large amount of CuHf phase will be obtained in the matrix, the CuHf phase will precipitate in various morphologies (rod-shaped, spherical, and disc-shaped) and grow and coarsen during the aging process, which greatly weakens the strengthening effect of the matrix. The inventors have found that the regression process can not only refine the grains, but also interrupt the precipitation process of the CuHf phase and regulate the precipitation order, thereby retaining the strengthening effect provided by the nanoscale CuHf phase to the greatest extent. Finally, under the synergistic effect of the trace additive elements of the present invention, the CuHf phase and the Cr phase can be dispersed in the matrix in the form of nano-spherical phases, achieving a more excellent strengthening effect.

[0022] The above-mentioned preparation method allows high-density nanoscale Cr and CuHf phases to serve as the alloy's primary strengthening secondary phases, dispersively distributed in the matrix. These phases interact with fine grains and a high density of dislocations, forming a microstructural characteristic of multi-mechanism synergistic strengthening, thereby endowing the prepared CuCrHf alloy with excellent mechanical properties, electrical conductivity, and softening resistance. On the one hand, the aging + cold deformation + regression process causes some solid-solution elements to initially dissolve from the matrix, becoming a source of dislocation proliferation during subsequent deformation and a nucleation point and pinning point for grain boundaries during regression. This increases the dislocation density introduced into the matrix by cold deformation and reduces the size of recrystallized grains. The initial grain size of the alloy is significantly superior to that of the untreated solid-solution alloy. On the other hand, the Cr and Hf elements dissolved in the matrix can be eluted from the copper alloy solid solution after cold deformation and heat treatment, and evenly dispersed in the matrix, providing a synergistic solid solution strengthening effect of trace Ag and Zn elements on the matrix, so that the alloy has excellent electrical conductivity while also exhibiting excellent mechanical properties and softening resistance.

[0023] In a preferred embodiment, the smelting process is as follows: pure copper, Cu-Cr master alloy, Cu-Hf master alloy, Cu-Zn master alloy, Cu-P master alloy, pure Ce, pure Ag, and pure Zn are prepared according to the designed proportions; the pure copper is first melted, then the temperature is raised to 1200-1300°C, pure Ag and pure Zn are added, the temperature is continued to be raised to 1300-1400°C, the Cu-Cr master alloy is added in 3-4 batches, the temperature is kept for 2-3 minutes, and then the mixture is stirred for 30-60 seconds; then, the Cu-Hf master alloy, pure Ce, and Cu-P master alloy are added, the temperature is kept for 1-2 minutes, and the temperature is lowered to 1200-1300°C while stirring.

[0024] In the present invention, the alloying elements are relatively numerous, and the material addition sequence of the preferred embodiment can effectively reduce the burnout of the alloying elements. In addition, due to the relatively large number of alloying elements added, the viscosity of the melt is relatively high during the smelting process, and slag is easily generated. The added Cu-P master alloy can be combined with the stirring operation after the step-by-step addition to effectively alleviate this problem, purify the melt, improve the fluidity of the melt, and thus improve the quality of the ingot. The stirring during the smelting process can, on the one hand, promote the full melting of the gradually added alloying elements and make the composition of the molten metal uniform. On the other hand, it can also alleviate the cooling effect of the step-by-step addition on the local melt.

[0025] In actual operation, a medium frequency induction furnace is used for melting in an atmospheric atmosphere, and a graphite rod is used for stirring during the melting process.

[0026] In a preferred embodiment, the smelting is carried out in an atmospheric atmosphere, and graphite is coated on the melt during the smelting process. By coating the melt with graphite as a deoxidizer, the burn-off rate can be reduced.

[0027] In a preferred embodiment, the casting temperature is 1200-1450°C, and the preheating temperature of the mold is 400-500°C.

[0028] In a preferred embodiment, the temperature of the homogenization annealing treatment is 780-980°C, and the homogenization annealing treatment time is 2-8 hours. The purpose of the homogenization annealing treatment is to eliminate the segregation phenomenon in the cast structure and eliminate the heterogeneity of the microstructure as much as possible. The effect of the homogenization annealing treatment is related to the selected system. If the temperature is too high, the alloy is prone to overburning or even melting, and the quality of the cast alloy may even decrease instead of improving. If the temperature is too low, the diffusion of elements is more difficult, and even if the holding time of the homogenization annealing treatment is increased, it is difficult to completely eliminate the intragranular segregation. The long homogenization time also increases the preparation process and process costs.

[0029] In a preferred embodiment, the thermal deformation treatment is selected from hot forging or hot rolling, the temperature of the thermal deformation treatment is 850-950° C., the total deformation is 50%-90%, and the deformation of each pass is 10%-20%.

[0030] In actual operation, after homogenization heat treatment, the homogenization annealed ingot is cooled in the furnace to the required temperature for hot deformation before hot deformation. Hot deformation is used to eliminate casting defects as much as possible, promote dynamic recrystallization of the alloy, and refine the coarse grains after casting and homogenization heat treatment.

[0031] In a preferred embodiment, the temperature of the solution treatment is 800-1050° C., the time of the solution treatment is 2-8 hours, and water quenching is performed after the solution treatment is completed.

[0032] All the added alloying elements are dissolved into the copper alloy matrix through solution treatment, and the supersaturated solid solution state is retained at room temperature through water quenching to provide sufficient precipitation power.

[0033] In a preferred embodiment, the pre-aging temperature is 350-600° C., and the pre-aging time is 5-480 minutes.

[0034] After solution treatment, the alloy has sufficient precipitation momentum. After aging, a considerable amount of nanoscale CuHf and Cr phases are formed within the alloy. Combined with subsequent deformation and regression treatment, this results in better precipitation and grain refinement. In practice, after aging, surface defects in the alloy need to be removed and corrected through machining.

[0035] In a preferred solution, the total deformation amount of the pre-cooling deformation treatment is 40% to 90%, and the deformation amount of each pass is in the range of 10% to 30%.

[0036] In a preferred embodiment, the temperature of the regression treatment is 750-1000° C., and the treatment time is 10 s-10 min.

[0037] The purpose of the regression treatment is to combine the high-density nanophase precipitated during pre-aging with the high-density dislocations introduced during the pre-cold deformation process, causing widespread recrystallization of the alloy, resulting in finer grains and a greater contribution to the alloy's strength. This, in turn, interrupts the precipitation process of the CuHf phase, thereby maximizing the strengthening effect provided by the nanoscale CuHf phase. The regression treatment temperature must be within a set range. If the regression temperature is too low, not only will the recrystallization effect be lost, but it will only regulate the formation of precipitated phases. If the regression temperature is too high, secondary recrystallization will occur, failing to achieve grain refinement and returning the alloy's structure to the solution-treated state.

[0038] In a preferred embodiment, the combined thermomechanical treatment consists of alternating cold deformation and aging treatments. In actual operation, the amount and frequency of cold deformation, as well as the temperature, duration, and frequency of aging, can be controlled, and the properties of the alloys produced by different treatment regimes vary. If both the number of cold deformation and aging cycles is one, the cold deformation should be 40% to 90%, and the aging temperature and duration should be 350-600°C for 5-480 minutes.

[0039] Further preferably, the combined thermomechanical treatment consists of two cold deformations and two aging treatments, wherein the deformation amount of the first cold deformation is 40% to 90%, and the deformation amount of each pass is 10% to 30%. After the first cold deformation treatment, the first aging treatment is performed, and then the second cold deformation treatment is performed. The deformation amount of the second cold deformation treatment is 40% to 90%, and the deformation amount of each pass is 10% to 30%. After the second cold deformation treatment, the second aging treatment is performed, wherein the temperature of the first aging treatment is 350 to 600° C., preferably 450 to 500° C., and the time is 5 to 480 min. The temperature of the second aging treatment is 350 to 600° C., preferably 350 to 450° C., and the time is 5 to 480 min.

[0040] After the regression treatment, combined deformation heat treatment is performed, and finally a large number of nano-spherical CuHf phases and Cr phases are precipitated and dispersed in the matrix, thereby obtaining a high-strength and high-conductivity copper alloy with the most excellent comprehensive performance.

[0041] The positive beneficial effects achieved by the present invention are:

[0042] (1) According to the preparation and processing technology specified in the present invention, the copper alloy plate prepared after a series of treatments has a conductivity of 70-89% IACS, a hardness of 180-230 HV, a tensile strength of 670-730 MPa, and an elongation of 8.2%-16.7%. While significantly improving the strength of the alloy system, it also has excellent plasticity and electrical conductivity. Compared with other high-strength and high-conductivity copper alloys, the alloy prepared by the present invention has excellent comprehensive mechanical properties, enriching my country's product library of high-strength and high-conductivity copper alloys.

[0043] (2) The strengthening idea of ​​modifying the precipitated phase with alloying elements was changed. By adding Hf elements that form a single-phase solid solution zone with Cu and Cr, and combining the deformation heat treatment process to control the alloy structure, a composite strengthening effect of two nano-scale strengthening phases was achieved, which greatly improved the comprehensive performance of the alloy and achieved a higher combination of strength and conductivity.

[0044] (3) Improve the overall performance while maintaining the high electrical conductivity of the alloy as much as possible. The fundamental reason lies in the regulation of the microstructure by the alloying elements Hf, P, Ce, Zn, and Ag. The addition of Hf, Zn, and Ag has the effect of reducing the stacking fault energy of the alloy, so that the alloy forms deformation twins during conventional cold rolling deformation, improves the strength of the alloy, and can effectively improve the hardening effect of the alloy during subsequent deformation; the P element can purify the melt and make the melt fluidity of the alloy better, and the quality of the alloy ingot obtained by casting is higher; the Ce element can refine the grains.

[0045] (4) The preparation method of pre-aging + pre-cold deformation + regression process + combined deformation heat treatment can maximize the precipitation potential of the alloy. The precipitation phase of the first aging precipitation can pin the dislocations, and a large number of dislocations can be introduced into the matrix by combining the subsequent cold deformation. The mechanical properties of the alloy are improved by deformation strengthening, precipitation strengthening and a small part of solid solution strengthening. More importantly, the CuHf phase order is regulated by the above process, and finally a large number of nano-spherical CuHf phases and Cr phases are precipitated and dispersed in the matrix, thereby obtaining a high-strength and high-conductivity copper alloy with the best comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is the preparation process flow of the new high-strength and high-conductivity copper alloy material described in the present invention.

[0047] Figure 2 This is the EBSD result of the copper alloy after solution treatment in Example 1 of the present invention.

[0048] Figure 3 This is the EBSD result of the sample after the copper alloy regression treatment in Example 1 of the present invention.

[0049] Figure 4 This is the hardness change curve of the copper alloy after combined deformation heat treatment in Example 1 of the present invention.

[0050] Figure 5 This is the conductivity change curve of the copper alloy after combined deformation heat treatment in Example 1 of the present invention.

[0051] Figure 6 This is a bright field image of the copper alloy during peak aging in Example 1 of the present invention. DETAILED DESCRIPTION

[0052] The present invention provides a high-strength, high-conductivity copper alloy material comprising appropriate amounts of Cr, Hf, P, Ce, Zn, and Ag, capable of achieving excellent overall performance. The present invention also provides a process for preparing the high-strength, high-conductivity copper alloy material.

[0053] In order to better understand the above solution, the present invention is described in detail below in conjunction with the embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein.

[0054] Example 1

[0055] Example 1 A high-strength and high-conductivity copper alloy material was prepared. The material components, in mass percentage, included 0.7 wt.% Cr, 0.9 wt.% Hf, 0.02 wt.% P, 0.01 wt.% Ce, 0.01 wt.% Zn, 0.02 wt.% Ag, and the balance was copper.

[0056] The preparation method of the high-strength and high-conductivity copper alloy selected in Example 1 includes the following steps:

[0057] 1) Ingots were melted in a medium frequency induction melting furnace in an atmospheric environment. The raw materials for the smelting were a Cu-10 wt.% Cr master alloy, a Cu-20 wt.% Hf master alloy, a Cu-20 wt.% Zn master alloy, a Cu-10 wt.% P master alloy, pure Ce, pure Ag, and pure Zn. The raw materials, crucible, and mold were fully preheated to 150° C. for the raw materials and 500° C. for the crucible and mold to ensure thorough drying.

[0058] There are relatively strict requirements for the feeding sequence in the smelting process, and the quality of the ingot can be effectively improved and guaranteed: first put pure copper into the crucible, start heating, and wait for it to melt (1083℃). When the melt temperature is 1250℃, add pure Ag and pure Zn. When the melt temperature rises to 1400℃, add Cu-Cr master alloy in 3 to 4 batches. After each batch of feeding, keep it warm for 2 minutes and stir it for 60 seconds. Cover the surface of the melt with graphite, then add Cu-Hf master alloy, pure Ce, and Cu-P master alloy. Keep it warm for 2 minutes, stir it for 60 seconds, and pour it after the melt temperature drops to 1250℃.

[0059] 2) The smelted ingot is homogenized and kept at 950°C for 4 hours.

[0060] 3) After the ingot is cooled to 900°C in the furnace, the homogenized billet is subjected to hot working by hot rolling. The total deformation of the hot rolling is 80%, which is completed in five passes with a deformation of 16% per pass. After hot rolling, the billet is water quenched.

[0061] 4) The alloy after hot deformation and blanking is solution treated at a solution temperature of 950°C, a holding time of 2 h, and water quenching.

[0062] 5) The alloy after solution treatment is pre-aged at a temperature of 500°C, a pre-aging time of 60 min, and a cooling method of water quenching.

[0063] 6) The pre-aged alloy is pre-cold deformed by cold rolling with a deformation of 40% in three passes, with each pass deformation controlled between 10% and 15%.

[0064] 7) The pre-aged alloy is subjected to regression treatment at 750°C for 5 minutes and water quenching as the cooling method.

[0065] 8) The alloy which has completed grain refinement is subjected to a combined deformation heat treatment, which consists of two deformations and two aging. The plate is subjected to one cold rolling at room temperature, the total deformation of which is 80%, and is completed in three passes, the pass deformation being controlled to be between 10% and 30%, and is subjected to one aging in a furnace at 450 DEG C for 2 hours; the plate is subjected to two cold rolling at room temperature, the total deformation of which is 50%, and is completed in three passes, the pass deformation being controlled to be between 15% and 20%, and is subjected to two aging in a furnace at 350 DEG C for 12 hours, thereby obtaining the new high-strength high-conductivity copper alloy material researched in the application.

[0066] Figure 1 The preparation process route of the embodiment of the application.

[0067] Figure 2 The EBSD result of the embodiment 1 after solid solution treatment shows that the grain size is large after the solid solution treatment, and is about 300-400 μm.

[0068] Figure 3 The EBSD result of the embodiment 1 after a series of grain refinement processes (pre-aging, pre-cold deformation and regression treatment) shows that the grains have generally undergone recovery recrystallization, and the grain size has been effectively refined, and is about 10-30 μm.

[0069] Figure 4 and Figure 5 The aging hardness and conductivity change curve of the embodiment 1 after the combined deformation heat treatment shows that the alloy has obvious strengthening effect.

[0070] Figure 6 The TEM observation result of the precipitated phase in the peak aging state shows that the alloy matrix is distributed with fine and dispersed precipitated phase, and has obvious interaction with dislocations, which indicates that the nanoscale precipitated phase particles can effectively pin the migration of dislocations, and improve the strength and toughness of the alloy. The tensile strength of the final product is 760 MPa, the hardness is 235 HV, and the conductivity is 73% IACS.

[0071] The high-strength high-conductivity copper alloy material prepared in the embodiment 1 is subjected to physical property test, and the test result is shown in Table 1.

[0072] Table 1 Physical properties of the embodiment 1

[0073] Physical properties Test results Test Method Room temperature hardness 235HV YS / T471-2004 Room temperature tensile strength 760MPa GB / T34505-2017 Room temperature elongation 11.3％ GB / T34505-2017 Room temperature conductivity 73% IACS GB / T32791-2016

[0074] Embodiment 2

[0075] Example 2: A high-strength and high-conductivity copper alloy material was prepared. The material components, in mass percentage, included 0.4 wt.% Cr, 0.6 wt.% Hf, 0.02 wt.% P, 0.02 wt.% Ce, 0.02 wt.% Zn, 0.01 wt.% Ag, and the balance was copper.

[0076] The preparation method of the high-strength and high-conductivity copper alloy selected in Example 2 includes the following steps:

[0077] 1) Ingots were melted in a medium frequency induction melting furnace in an atmospheric environment. The raw materials for the smelting were a Cu-10 wt.% Cr master alloy, a Cu-20 wt.% Hf master alloy, a Cu-20 wt.% Zn master alloy, a Cu-10 wt.% P master alloy, pure Ce, pure Ag, and pure Zn. The raw materials, crucible, and mold were fully preheated to 150°C for the raw materials and 400°C for the crucible and mold to ensure thorough drying.

[0078] The order of feeding materials in the smelting process has not changed: first put pure copper into the crucible, start heating, and wait for it to melt (1083℃). When the melt temperature is 1250℃, add pure Ag and pure Zn. When the melt temperature rises to 1400℃, add Cu-Cr master alloy in 3 to 4 batches. After each batch of feeding, keep warm for 2 minutes and stir for 60 seconds, and cover the surface of the melt with graphite. Then add Cu-Hf master alloy, pure Ce, and Cu-P master alloy, keep warm for 2 minutes, stir for 60 seconds, and pour after the melt temperature drops to 1250℃.

[0079] 2) The smelted ingot is homogenized and kept at 950°C for 2 hours.

[0080] 3) After the ingot is cooled to 900°C in the furnace, the homogenized billet is subjected to hot working by hot rolling. The total deformation of the hot rolling is 80%, which is completed in five passes with a deformation of 16% per pass. After hot rolling, the billet is water quenched.

[0081] 4) The alloy after hot deformation and blanking was solution treated at a solution temperature of 950°C, a holding time of 1 h, and water quenching.

[0082] 5) The alloy after solution treatment is pre-aged at a temperature of 500°C, a pre-aging time of 30 min, and a cooling method of water quenching.

[0083] 6) The pre-aged alloy is pre-cold deformed by cold rolling with a deformation of 40% in three passes, with each pass deformation controlled between 10% and 15%.

[0084] 7) The pre-aged alloy is subjected to regression treatment at 750°C for 5 minutes and water quenching as the cooling method.

[0085] 8) The alloy after grain refinement is subjected to combined deformation heat treatment, which consists of two deformations and two aging. The plate is subjected to one cold rolling at room temperature, the total deformation amount of cold rolling is 80%, which is completed in three passes, the pass deformation amount is controlled in the middle of 10%~30%, and one aging is carried out in a furnace at 450℃, the aging time is 1h; the second cold rolling is carried out at room temperature, the total deformation amount of cold rolling is 50%, which is completed in three passes, the pass deformation amount is controlled in the middle of 15%~20%, and the second aging is carried out in a furnace at 350℃, the aging time is 12h, thereby obtaining the new high-strength high-conductivity copper alloy material studied in the application.

[0086] The high-strength high-conductivity copper alloy material prepared in Example 2 is subjected to physical property testing, the tensile strength of the final product is 673MPa, the hardness is 206HV, and the conductivity is 72%IACS, and the test results are shown in Table 2.

[0087] Table 2 Physical properties of Example 2

[0088] Physical properties Test results Test Method Room temperature hardness 206HV YS / T471-2004 Room temperature tensile strength 673MPa GB / T34505-2017 Room temperature elongation 14.7％ GB / T34505-2017 Room temperature conductivity 72% IACS GB / T32791-2016

[0089] Comparative Example 1

[0090] The CuCrHf alloy material prepared in Comparative Example 1 has the same components as Example 1, the raw material preparation and melting process in the preparation method are the same as those in Example 1, and the specific treatment process is as follows:

[0091] 1) The raw material preparation and melting are the same as those in Example 1.

[0092] 2) The ingot after melting is subjected to homogenization treatment at 950℃ for 4h.

[0093] 3) After the ingot is cooled to 900℃ in the furnace, the homogenized blank is subjected to hot working in the form of hot rolling, the total deformation amount of hot rolling is 80%, which is completed in five passes, the pass deformation amount is 16%, and the hot rolling is completed and then water quenched.

[0094] 4) The alloy after hot deformation breakdown is subjected to solid solution treatment at a solid solution temperature of 950℃ for 2h and then water quenched.

[0095] 5) The alloy after grain refinement is subjected to combined deformation heat treatment, which consists of two deformations and two aging. The plate is subjected to one cold rolling at room temperature, the total deformation amount of cold rolling is 80%, which is completed in three passes, the pass deformation amount is controlled in the middle of 10%~30%, and one aging is carried out in a furnace at 450℃, the aging time is 2h; the second cold rolling is carried out at room temperature, the total deformation amount of cold rolling is 50%, which is completed in three passes, the pass deformation amount is controlled in the middle of 15%~20%, and the second aging is carried out in a furnace at 350℃, the aging time is 12h.

[0096] The physical properties of the high-strength and high-conductivity copper alloy material prepared in Comparative Example 1 were tested. The final product had a tensile strength of 614 MPa, a hardness of 190 HV, and a conductivity of 76% IACS. The test results are shown in Table 3.

[0097] Table 3 Physical properties of Comparative Example 1

[0098] Physical properties Test results Test Method Room temperature hardness 190HV YS / T471-2004 Room temperature tensile strength 614MPa GB / T34505-2017 Room temperature elongation 16.9％ GB / T34505-2017 Room temperature conductivity 76% IACS GB / T32791-2016

[0099] By comparing the test results of Example 1 with those of Comparative Example 1, it can be seen that the overall comprehensive performance of Comparative Example 1 has been significantly reduced, and this difference is mainly caused by the grain refinement treatment process (the final grain size of Example 1 is 3-8 μm, while that of the comparative example is 6-13 μm), indicating that the combination of pre-aging, pre-cooling deformation and regression process can effectively regulate the precipitation order of the precipitated phase, refine the grain size of the alloy, and improve the comprehensive performance of the alloy.

[0100] Comparative Example 2

[0101] The composition of the CuCrHf alloy material prepared in Comparative Example 2 is the same as that in Example 2. The raw material preparation and smelting process in its preparation method are the same as those in Example 1. The specific processing process is as follows:

[0102] 1) Raw material preparation and smelting are the same as in Example 2.

[0103] 2) The smelted ingot is homogenized and kept at 950°C for 2 hours.

[0104] 3) After the ingot is cooled to 900°C in the furnace, the homogenized billet is subjected to hot working by hot rolling. The total deformation of the hot rolling is 80%, which is completed in five passes with a deformation of 16% per pass. After hot rolling, the billet is water quenched.

[0105] 4) The alloy after hot deformation and blanking was solution treated at a solution temperature of 950°C, a holding time of 1 h, and water quenching.

[0106] 5) The grain-refined alloy undergoes a combined thermomechanical treatment consisting of two deformations and two aging cycles. The plate undergoes a single cold rolling process at room temperature, with a total cold rolling deformation of 80% in three passes, each with a deformation range of 20% to 30%. The plate undergoes a primary aging process in a 450°C furnace for one hour. The plate undergoes a secondary cold rolling process at room temperature, with a total cold rolling deformation of 50% in three passes, each with a deformation range of 15% to 20%. The plate undergoes a secondary aging process in a 350°C furnace for 12 hours, resulting in the novel high-strength, high-conductivity copper alloy material studied in the present invention.

[0107] The physical properties of the high-strength and high-conductivity copper alloy material prepared in Comparative Example 2 were tested. The final product had a tensile strength of 591 MPa, a hardness of 174 HV, and a conductivity of 79% IACS. The test results are shown in Table 4.

[0108] Table 4 Physical properties of Comparative Example 2

[0109] Physical properties Test results Test Method Room temperature hardness 174HV YS / T471-2004 Room temperature tensile strength 591MPa GB / T34505-2017 Room temperature elongation 18.9％ GB / T34505-2017 Room temperature conductivity 79% IACS GB / T32791-2016

[0110] By comparing the test results of Example 2 with those of Comparative Example 2, it is once again verified that the combination of pre-aging, pre-cooling deformation and regression process can effectively regulate the precipitation order of the precipitated phase, refine the grains of the alloy, and improve the comprehensive properties of the alloy.

Claims

1. A method for preparing a high-strength and high-conductivity copper alloy material, characterized by: First, the raw materials are mixed according to the designed composition ratio, smelted to obtain alloy liquid, and the alloy liquid is cast to obtain a copper alloy ingot. The copper alloy ingot is then subjected to homogenization annealing treatment, thermal deformation treatment, and solid solution treatment in sequence to obtain a solid solution alloy material. Finally, the solid solution alloy material is subjected to pre-aging treatment, pre-cold deformation treatment, regression treatment, and combined thermomechanical treatment in sequence to obtain a high-strength and high-conductivity copper alloy material. The pre-aging temperature is 350-600°C, and the pre-aging time is 5-480 minutes; The total deformation of the pre-cooling deformation treatment is 40% to 90%, and the deformation of each pass is 10% to 30%; The temperature of the regression treatment is 750-1000°C, and the time of the regression treatment is 10s-10min; The copper alloy material has the following composition, calculated by mass percentage: Cr 0.4-1.5 wt.%, Hf 0.6-1.5 wt.%, P0-0.02 wt.%, Ce 0-0.15 wt.%, Zn 0-0.2 wt.%, Ag 0-0.2 wt.%, and the balance is Cu.

2. The method for preparing a high-strength and high-conductivity copper alloy material according to claim 1, characterized in that: The smelting process comprises the following steps: preparing pure copper, Cu-Cr master alloy, Cu-Hf master alloy, Cu-Zn master alloy, Cu-P master alloy, pure Ce, pure Ag and pure Zn according to a designed proportion; firstly melting the pure copper, then heating the mixture to 1200-1300° C., adding pure Ag and pure Zn, and continuing to heat the mixture to 1300-1400° C., adding the Cu-Cr master alloy in 3-4 batches, keeping the temperature for 2-3 minutes, stirring the mixture for 30-60 seconds, then adding the Cu-Hf master alloy, pure Ce and Cu-P master alloy, keeping the temperature for 1-2 minutes, and then cooling the mixture to 1200-1300° C. while stirring.

3. The method for preparing a high-strength and high-conductivity copper alloy material according to claim 1 or 2, characterized in that: The smelting is carried out in an atmospheric atmosphere. During the smelting process, graphite is covered on the melt. The temperature of the casting is 1200-1450°C, and the preheating temperature of the mold is 400-500°C.

4. The method for preparing a high-strength and high-conductivity copper alloy material according to claim 1 or 2, characterized in that: The homogenization annealing treatment temperature is 780-980°C, and the homogenization annealing treatment time is 2-8 hours; The thermal deformation treatment is selected from hot forging or hot rolling, the temperature of the thermal deformation treatment is 850-950°C, the total deformation is 50%-90%, and the deformation of each pass is 10%-20%; The temperature of the solution treatment is 800-1050° C., the time of the solution treatment is 2-8 hours, and water quenching is performed after the solution treatment is completed.

5. The method for preparing a high-strength and high-conductivity copper alloy material according to claim 1 or 2, characterized in that: The combined deformation heat treatment consists of alternating cold deformation treatment and aging treatment.

6. The method for preparing a high-strength and high-conductivity copper alloy material according to claim 5, characterized in that: The combined thermomechanical treatment consists of two cold deformations and two aging treatments, wherein the deformation amount of the first cold deformation is 40% to 90%, and the deformation amount of each pass is 10% to 30%. After the first cold deformation treatment, the first aging treatment is performed, and then the second cold deformation treatment is performed. The deformation amount of the second cold deformation treatment is 40% to 90%, and the deformation amount of each pass is 10% to 30%. After the second cold deformation treatment, the second aging treatment is performed. The temperature of the first aging treatment is 350 to 600° C. and the time is 5 to 480 minutes. The temperature of the second aging treatment is 350 to 600° C. and the time is 5 to 480 minutes.

7. The method for preparing a high-strength and high-conductivity copper alloy material according to claim 1 or 2, characterized in that: The copper alloy material has the following composition, calculated by mass percentage: Cr 0.4-0.7 wt.%, Hf 0.6-0.9 wt.%, P 0-0.02 wt.%, Ce 0-0.02 wt.%, Zn 0-0.02 wt.%, Ag 0-0.2 wt.%, and the balance is Cu.

8. The method for preparing a high-strength and high-conductivity copper alloy material according to claim 1 or 2, characterized in that: In the high-strength and high-conductivity copper alloy material, multiple nanoscale precipitated phases and dislocations interact with each other, are pinned and entangled with each other, and are dispersed in the matrix. The grain size of the high-strength and high-conductivity copper alloy material is ≤30μm, and twins are contained in the grains.

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