Cu-Be-Ni-Co-Mg series alloy with high strength and high stress relaxation resistance and preparation method of Cu-Be-Ni-Co-Mg series alloy

Abstract

The invention discloses a Cu-Be-Ni-Co-Mg alloy with high strength and high stress relaxation resistance and a preparation method of the Cu-Be-Ni-Co-Mg alloy, and the Cu-Be-Ni-Co-Mg alloy comprises the following components in percentage by mass: 0.6-1.6 wt% of Be, 0.5-1.5 wt% of Ni, 0.5-1.5 wt% of Mg, 0.5-1.5 wt% of Ni, 0.5-1.5 wt% of Mg, and the balance 0 to 0.7 wt% of Ni, 0 to 0.7 wt% of Co, 0.05 to 0.5 wt% of Mg, with 0 lt; ni + Co < lt >; the preparation method comprises the steps that a cast ingot obtained through smelting is subjected to homogenization treatment and solution treatment to obtain a solid solution blank, the solid solution blank is subjected to hot rolling treatment to obtain a hot rolling blank, then the hot rolling blank is subjected to multi-stage aging treatment, the tensile strength is 900-1400 MPa, the elastic modulus is 130-140 GPa, the electric conductivity is 25%-35% IACS, and the stress relaxation rate at 200 DEG C / 1000 h is smaller than or equal to 8%.

Description

Technical Field

[0001] The present invention belongs to the technical field of beryllium copper alloy preparation, and particularly relates to a Cu-Be-Ni-Co-Mg alloy with high strength and high stress relaxation resistance and a preparation method thereof. Background Art

[0002] Beryllium copper alloy plays an irreplaceable role in key fields such as electronic communication and aerospace due to its excellent high strength, high conductivity, high elasticity and wear resistance, and is an important basic material for the national economy and national defense industry. According to the difference in beryllium content, the existing beryllium copper alloys can be divided into low-beryllium high-conductivity type (Be: 0.2wt% - 0.6wt%) and high-beryllium high-strength type (Be: 1.8wt% - 2.2wt%). However, there are still significant technical bottlenecks in the existing beryllium copper material system: 1) High-beryllium alloys are severely restricted in their large-scale application due to the high cost of Be element and the environmental toxicity risk during the processing; 2) Low-beryllium alloys are limited by the strong correlation between beryllium content and strength, and their mechanical properties and wear resistance are difficult to meet the stringent requirements of high-end electronic devices; 3) Existing alloys generally have stress relaxation failure problems in the medium-temperature service environment (100 - 300°C), which directly affects the reliability of precision electronic systems and long-life equipment, and becomes the core technical obstacle restricting industrial upgrading. Therefore, it is of great scientific significance and engineering value to develop medium-beryllium content beryllium copper alloys with excellent mechanical properties, high stress relaxation resistance and environmental friendliness. In order to reduce the Be content and maintain the performance, current research mainly uses inexpensive alloy elements to partially replace Be. However, existing research mostly focuses on the influence of single Ni and Co elements, and the research on the synergistic effect of multiple elements is insufficient, especially the systematic discussion on the effect of alloy elements on stress relaxation resistance is lacking, and the related mechanisms and regulation methods need to be further studied. In addition, the performance of beryllium copper alloy highly depends on the morphology and distribution of the aging precipitation phases. Traditional aging processes are prone to form coarse and discontinuous precipitation phases (such as over-aged γ-CuBe phase), which damage the strength, toughness and stress relaxation resistance, and exacerbate the sensitivity of grain boundary corrosion. The precipitation phase evolution behavior of high-beryllium alloys (Be: 1.8 - 2.2wt%) is more complex, and the traditional solution-aging process is difficult to accurately control the continuity of precipitation phases, restricting the performance stability. Therefore, optimizing the preparation process and realizing the fine control of precipitation phases are the keys to improving the comprehensive performance of beryllium copper alloys. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the first object of the present invention is to provide a Cu-Be-Ni-Co-Mg alloy with high strength and high stress relaxation resistance. The Cu-Be-Ni-Co-Mg alloy provided by the present invention has high strength, high conductivity and excellent stress relaxation resistance while moderately reducing the Be content and using less noble metals.

[0004] The second object of the present invention is to provide a preparation method of a Cu-Be-Ni-Co-Mg alloy with high strength and high stress relaxation resistance. The preparation method of the present invention is simple, controllable, and low in cost, and is suitable for large-scale industrial production.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a Cu-Be-Ni-Co-Mg alloy with high strength and high stress relaxation resistance. The Cu-Be-Ni-Co-Mg alloy has the following composition by mass percentage: Be: 0.6 - 1.6 wt%; Ni: 0 - 0.7 wt%, Co: 0 - 0.7 wt%, Mg: 0.05 - 0.5 wt%, where 0 < Ni + Co < 1 wt%, and the balance is Cu and inevitable impurities.

[0007] In the Cu-Be-Ni-Co-Mg alloy of the present invention, the content of Be is appropriately reduced, and a trace amount of Mg element is added. The trace Mg element preferentially segregates at the grain boundaries, effectively inhibiting the nucleation and growth of discontinuous precipitation phases (such as grain boundary γ phase), while reducing the grain boundary energy, refining the size of the precipitation phases, and blocking the slip channels of dislocations along the grain boundaries during the high-temperature stress relaxation process, thereby improving the stress relaxation resistance of the alloy; while Ni and / or Co participate in the precipitation process of Be synergistically to form high-density nano-scale composite precipitation phases (NiBe / CoBe, size ≤ 15 nm), which significantly improve the matrix strength by pinning dislocations and suppressing lattice distortion; at the same time, the introduction of Mg can reduce the diffusion rate of Be atoms, delay the coarsening of over-aged γ phase, and ensure the tissue stability in the medium-temperature environment. In addition, the solid-solution atoms of Ni and Co form short-range ordered clusters with Be, reducing the negative impact of lattice distortion on the conductivity while improving the matrix strength; the solid solution of Mg further refines the grains, realizing the synergistic optimization of strength and plasticity.

[0008] The Cu-Be-Ni-Co-Mg alloy of the present invention significantly reduces the production cost and environmental health risks by means of reducing the beryllium content, reducing the consumption of precious metals, and optimizing the element ratio.

[0009] In the present invention, it is necessary to precisely control the contents of Ni, Co, and Mg elements and their synergistic ratio with Be in order to achieve the coupling of multi-dimensional strengthening mechanisms. On the one hand, Ni / Co enhances the alloy aging precipitation ability by reducing the solid solubility of Be element, while appropriate amount of Mg complements it by dynamically regulating the high-temperature solubility, which can increase the solid solubility of Be element at high temperature to a certain extent without affecting the low-temperature solid solubility, and can increase the number of precipitation phases after alloy aging, and synergistically improve the precipitation strengthening ability of the alloy. On the other hand, Ni / Co inhibits the grain boundary segregation of Be atoms by capturing Be atoms (forming NiBe phase or CoBe phase), and Mg preferentially occupies the grain boundary vacancies and reduces the grain boundary diffusion coefficient of Be atoms (the binding energies of Be, Mg, and Ni elements with vacancies are -0.01 eV, -0.19 eV, and 0.06 eV respectively). The coupling effect of the two promotes the precipitation behavior of the alloy to change from the discontinuous precipitation dominated by grain boundaries to the continuous precipitation mechanism dominated by intragranular regions (resulting in an increase in the number of nanoscale precipitation phases). The synergistic effect of Ni and Mg elements significantly inhibits the discontinuous precipitation phenomenon of the alloy, increases the number of intragranular precipitation phases and the tissue uniformity, the increase in the number of nanoscale precipitation phases and the reduction of coarse grain boundary precipitation phases inhibit the dislocation movement and the recrystallization process, thereby greatly improving the stress relaxation resistance of the alloy.

[0010] However, if the content of Ni / Co is too high, on the one hand, the solid solubility of Be in Cu decreases significantly, and Be atoms cannot be fully dissolved in the copper matrix, so the number of subsequent precipitation phases will naturally decrease significantly. On the other hand, it will cause serious primary phases (NiBe phase, CoBe phase). These coarse primary phases are prone to act as crack initiation sources during the service of the material, deteriorating the mechanical properties of the alloy; at the same time, it will also cause serious electron scattering, deteriorating the electrical conductivity of the alloy. And too high content of Mg element will form Cu 2 Mg compounds at the grain boundaries. This kind of compound is a brittle phase and is prone to act as a crack initiation source during the service of the material, deteriorating the alloy properties; in addition, the enrichment of excessive Mg atoms at the grain boundaries forms new nucleation sites for Be atoms in the alloy. The concentration of Be atoms around these Mg atoms is slightly higher than that in the intragranular region but lower than the concentration condition required for discontinuous precipitation. Therefore, the rate of continuous transformation in these regions is faster than that in the intragranular region, and finally coarse discontinuous precipitation phases are quickly formed at the grain boundaries. These coarse discontinuous phases are prone to act as crack initiation sources during the service of the material, deteriorating the mechanical properties of the alloy. At the same time, the formation of coarse discontinuous precipitation phases consumes a large number of Be atoms, resulting in a significant decrease in the number of nanoscale continuous precipitation phases in the intragranular region.

[0011] Preferably, for the Cu-Be-Ni-Co-Mg series alloy, by mass percentage, the composition is as follows: Be: 0.8~1.5 wt%, Ni: 0.1~0.7 wt%, Co: 0~0.5 wt%, Mg: 0.1~0.2 wt%, where Ni + Co < 1 wt%, and the balance is Cu and unavoidable impurities.

[0012] Further preferably, for the Cu-Be-Ni-Co-Mg series alloy, by mass percentage, the composition is as follows: Be: 1.2~1.5 wt%, Ni: 0.1~0.6 wt%, Co: 0~0.3 wt%, Mg: 0.1~0.15 wt%, and the balance is Cu and unavoidable impurities.

[0013] Preferably, for the Cu-Be-Ni-Co-Mg series alloy, the tensile strength is 900~1400 MPa, the elastic modulus is 130~140 GPa, the conductivity is 25%~35% IACS, and the stress relaxation rate at 200 °C / 1000 h ≤ 8%. It can meet the stringent requirements for the comprehensive performance of materials in high-end fields such as aerospace precision relays, 5G high-frequency high-speed connectors, high-reliability defense electronic systems, and ultra-precision instruments and meters.

[0014] The present invention also provides a preparation method of a Cu-Be-Ni-Co-Mg series alloy with high strength and high stress relaxation resistance. Each component is proportioned and melted according to the design ratio to obtain an alloy ingot. The alloy ingot is subjected to homogenization treatment to obtain a homogenized billet. The homogenized billet is subjected to hot rolling treatment to obtain a hot-rolled billet. The hot-rolled billet is subjected to solution treatment to obtain a solution-treated billet. The solution-treated billet is successively subjected to pre-aging, first cold rolling, first aging, second cold rolling, second aging, and stress relief annealing to obtain the product.

[0015] The preparation method of the present invention adopts a multi-stage aging process. First, the pre-aging process helps to promote the uniform distribution of the nuclei of nano-scale precipitates, inhibit the formation of discontinuous precipitates (γ phase), refine the precipitate size, and eliminate the local stress concentration generated during hot rolling or solution treatment of the alloy, improve the uniformity of the alloy structure, lay a good structural foundation for subsequent aging treatment, and ultimately improve the stress relaxation resistance of the alloy. Then, through steps such as the main aging, it promotes the uniform nucleation and controllable growth of precipitates, avoids the formation of coarse precipitates, and ensures that nano-scale precipitates (such as BeCu, NiBe, CoBe, etc.) formed by elements such as Be, Ni, and Co are distributed in the matrix in a fine and continuous form, thereby improving the comprehensive performance of the alloy.

[0016] Preferably, the melting process is as follows: Electrolytic copper plates, Cu-Ni master alloy, Cu-Co master alloy, beryllium copper master alloy, and magnesium copper master alloy are placed in a vacuum melting furnace, and the vacuum is pumped to a vacuum degree ≤ 5×10﹣8 Pa, heat it to 1080 - 1350 °C for melting. After all the alloy raw materials are melted, pour the melt into a water-cooled mold for cooling to obtain an alloy ingot.

[0017] Furthermore, the mass percentage of nickel in the Cu-Ni master alloy is 10% - 45%, the mass percentage of cobalt in the Cu-Co master alloy is 10% - 35%, the mass percentage of beryllium in the beryllium copper master alloy is 3% - 6%, and the mass percentage of magnesium in the magnesium copper master alloy is 5% - 25%.

[0018] Furthermore, the homogenization treatment is carried out in a protective atmosphere. The temperature of the homogenization treatment is 800 - 950 °C, and the holding time is 4 - 8 h.

[0019] Furthermore, the temperature of the hot rolling is 850 - 900 °C. Before hot rolling, preheat and hold at 850 - 900 °C for 1 - 3 h, and hold at 850 - 900 °C for 15 - 30 min between passes.

[0020] In the present invention, through the preheating and holding before hot rolling, and the holding between passes, it is ensured that the hot rolling is carried out within the temperature range of the present invention. If the temperature is too low, it will cause the formation of coarse β-phase during the hot working of the alloy, seriously deteriorating the alloy properties.

[0021] Furthermore, the hot rolling is carried out in three passes. The total deformation amount of the hot rolling is 70% - 85%, and the deformation amounts of each pass are 35% - 40%, 20% - 35%, and 15% - 30% of the total deformation amount in sequence. In the present invention, through the decreasing rolling variables, the properties of the finally obtained material are optimal.

[0022] Furthermore, the temperature of the solution treatment is 780 - 950 °C, and the holding time is 15 min - 4 h. After the solution treatment is completed, water quench to room temperature. In the present invention, due to the incorporation of Ni / Co, the solid solubility of Be in copper decreases significantly. Therefore, a higher temperature is adopted for solution treatment to ensure the full solid solution of Be. Of course, the temperature cannot be too high, otherwise it will cause grain coarsening or even overburning.

[0023] Further, the pre-aging treatment is carried out in a salt bath, the temperature of the pre-aging treatment is 280-320°C, and the holding time is 5-60 min. In the present invention, the pre-aging treatment is first carried out after the solution treatment to promote the uniform nucleation of the nanoscale precipitation phase and inhibit the discontinuous precipitation phenomenon in the subsequent processing process. It can be seen that in the present invention, the temperature range of the pre-aging is relatively narrow. By precisely controlling the temperature and time parameters, the diffusion difference of Mg and Be atoms is used to achieve selective segregation. Under low temperature conditions, Mg atoms rely on higher diffusion activity and lower vacancy binding energy (the binding energy of Be, Mg, and Ni elements with vacancies is -0.01 eV, -0.19 eV, and 0.06 eV, respectively), so they preferentially migrate to the grain boundaries and form high-density clusters, while consuming vacancies at the grain boundaries, effectively avoiding the Be element from combining with vacancies at the grain boundaries to form clusters (the formation of Be atom clusters at the grain boundaries is a necessary condition for the generation of discontinuous precipitation phases). If the temperature is too high, the diffusion rates of Be atoms and Mg atoms to the grain boundaries may be similar, and the alloy will directly undergo rapid aging, forming discontinuous precipitation phases directly at the grain boundaries. In addition, experiments have found that the use of a salt bath can make the nano-precipitation phase more uniform.

[0024] Furthermore, the cold rolling is divided into three passes, the total deformation of the cold rolling is 70-80%, and the deformation of each pass is 30-35%, 20-30%, and 15-20% of the total deformation. In the present invention, the performance of the final material is optimal through the decreasing rolling variables.

[0025] Furthermore, the primary aging is carried out in a salt bath, the primary aging temperature is 325-450°C, and the insulation time is 1-8h. In the present invention, the primary aging is carried out in a salt bath to further promote the uniform distribution of the nanoscale precipitation phase and improve the strength and conductivity of the alloy. Of course, the primary aging temperature cannot be too high, otherwise it will cause Be atoms to precipitate quickly to form a discontinuous precipitation phase.

[0026] Furthermore, the secondary cold rolling is performed in two passes, the total deformation of the secondary cold rolling is 50-60%, and the deformation of each pass is 30-40% and 20-30% of the total deformation respectively.

[0027] Furthermore, the secondary aging is carried out in a salt bath, the temperature of the secondary aging is 300-400°C, and is not higher than the temperature of the primary aging, and the holding time is 0.5-3h, so as to further optimize the distribution of the precipitated phase and improve the stress relaxation resistance of the alloy.

[0028] By performing secondary aging in a salt bath, the temperature uniformity is ensured, the macroscopic uniformity of alloy precipitation is improved, the formation of discontinuous precipitation phases can be effectively avoided, and the stress relaxation resistance of the alloy is enhanced. Moreover, controlling the secondary cold rolling deformation amount to be lower than that of the primary cold rolling can make the material more uniform. At the same time, controlling the secondary aging temperature not to be higher than that of the primary aging can effectively prevent the growth of precipitation phases and deteriorate the alloy uniformity.

[0029] Furthermore, the temperature of the stress relief annealing is 180 - 300 °C, and the holding time is 1 - 2 h. Through the stress relief annealing treatment, the residual stress is eliminated, and the alloy dimensional stability and processing performance are improved.

[0030] Beneficial effects

[0031] 1. For the Cu-Be-Ni-Co-Mg series alloy of the present invention, the hardness is 300 - 420 HV, the tensile strength is 800 - 1400 MPa, the yield strength is 750 - 1200 MPa, the elastic modulus is 130 - 140 GPa, the conductivity is 25% - 35% IACS, and the stress relaxation rate at 200 °C / 1000 h is ≤ 8%. Compared with the existing high-beryllium alloys, the strength, conductivity, and stress relaxation resistance of the Cu-Be-Ni-Co-Mg series alloy of the present invention are increased by more than 5%, 30%, and 60% respectively. At the same time, the problems of environmental toxicity risk caused by high beryllium content, insufficient strength of low-beryllium alloys, and medium-temperature stress relaxation failure in the existing beryllium copper alloys are solved, and the synergistic optimization of high strength, high conductivity, and excellent stress relaxation resistance is achieved.

[0032] 2. The Cu-Be-Ni-Co-Mg series alloy of the present invention significantly reduces the production cost and environmental health risk by means of reducing the beryllium content, reducing the use of precious metals, and optimizing the element ratio. On the premise of ensuring that the alloy performance meets the service requirements and stability, the comprehensive manufacturing cost of the alloy of the present invention can be reduced by about 30% - 50%.

[0033] 3. The Cu-Be-Ni-Co-Mg series alloy of the present invention has excellent processability. By optimizing the hot rolling, cold rolling, aging process, and stress relief annealing process, there are no defects such as cracking and peeling during the processing of the alloy, the processing finished product rate is ≥ 95%, and the subsequent processing performances such as stamping, etching, and welding are good, which is suitable for the manufacture of complex precision parts.

[0034] 4. The Cu-Be-Ni-Co-Mg series alloy of the present invention can meet the stringent requirements for the comprehensive performance of materials in high-end fields such as aerospace precision relays, 5G high-frequency high-speed connectors, high-reliability defense electronic systems, and ultra-precision instruments and meters, providing a new material choice with high cost performance for high-end electronics, aerospace, and precision manufacturing fields. Brief description of the drawings

[0035] Figure 1 For the scanning microstructure at the grain boundaries of the Cu-Be-Ni-Co-Mg alloy in Example 1, it can be seen from the figure that no discontinuous precipitation basically occurred at the grain boundaries.

[0036] Figure 2 For the scanning microstructure at the grain boundaries of the QBe2.0 alloy in Comparative Example 1, it can be seen from the figure that serious discontinuous precipitation occurred at the grain boundaries, forming discontinuous precipitation phases distributed in lamellae. Specific Embodiments

[0037] The technical solutions of the present invention will be further described and illustrated below through specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are only used to assist in understanding the present invention and are not used for specific limitations of the present invention. And the accompanying drawings used herein are only for better illustrating the content disclosed by the present invention and do not have a limiting effect on the protection scope.

[0038] Example 1

[0039] The low-cost, high-strength, and high stress relaxation resistance Cu-Be-Ni-Co-Mg alloy and its preparation method in this example are as follows: Composition: Be: 1.5 wt%, Ni: 0.1 wt%, Co: 0.3 wt%, Mg: 0.1 wt%, and the balance is Cu.

[0040] The process flow is as follows:

[0041] (1) Melting: Place electrolytic copper plates, Cu-Ni master alloy (Ni: 30%), Cu-Co master alloy (Co: 20%), beryllium copper master alloy (Be: 4%), and magnesium copper master alloy (Mg: 15%) in a vacuum melting furnace, evacuate to a vacuum degree ≤ 5×10 - ³ Pa, heat to 1200 °C for melting, and pour the melt into a water-cooled mold for cooling after all the alloy raw materials are melted to obtain an alloy ingot.

[0042] (2) Homogenization treatment: Homogenize the alloy ingot at 850 °C for 6 h, and introduce argon for protection. After the treatment is completed, cool it with water.

[0043] (3) Hot rolling: Hot roll the homogenized alloy ingot after holding it at 850 °C for 1 h. The total hot rolling deformation is 80%, and it is rolled in three passes with deformation amounts of 35%, 30%, and 15% of the total deformation amount respectively. Keep it at 850 °C for 20 min between passes. After hot rolling, cool it with water to obtain an alloy sheet.

[0044] (4) Solution treatment: Quench the hot-rolled alloy sheet to room temperature after holding it at 850 °C for 1 h.

[0045] (5) Pre-aging treatment: The solution-treated alloy sheet is kept at 280 °C for 30 min in a salt bath furnace and then water-cooled.

[0046] (6) First cold rolling: The alloy sheet after pre-aging treatment is subjected to first cold rolling with a total deformation of 75%, divided into three passes, and the deformation of each pass is 30%, 20%, and 20% of the total deformation respectively.

[0047] (7) First aging treatment: The alloy sheet after first cold rolling is kept at 325 °C for 2 h in a salt bath furnace and then water-cooled.

[0048] (8) Second cold rolling: The alloy sheet after first aging treatment is subjected to second cold rolling with a total deformation of 60%, divided into two passes, and the deformation of each pass is 40% and 20% respectively.

[0049] (9) Second aging treatment: The alloy sheet after second cold rolling is kept at 325 °C for 1.5 h in a salt bath furnace and then water-cooled.

[0050] (10) Stress relief annealing treatment: The alloy sheet after second aging treatment is kept at 180 °C for 1.5 h to obtain a low-cost, high-strength, and high stress relaxation resistance Cu-Be-Ni-Co-Mg alloy. Figure 1 It is the scanning microstructure at the grain boundaries of the Cu-Be-Ni-Co-Mg alloy in Example 1. It can be seen from the figure that no discontinuous precipitation basically occurs at the grain boundaries, indicating that the Cu-Be-Ni-Co-Mg alloy prepared by the method described in the present invention can effectively inhibit the grain boundary reaction.

[0051] Example 2

[0052] The difference between this example and Example 1 is as follows:

[0053] (1) Hot rolling: After holding at 800 °C for 1 h, hot rolling is carried out with a total hot rolling deformation of 80%, divided into three passes, and the deformations are 35%, 30%, and 15% of the total deformation respectively. After hot rolling, water cooling is carried out to obtain an alloy sheet.

[0054] (2) First cold rolling: The total deformation is 80%, divided into three passes, and the deformation of each pass is 35%, 30%, and 15% respectively.

[0055] (3) Second cold rolling: The total deformation is 50%, divided into two passes, and the deformation of each pass is 30% and 20% respectively.

[0056] Example 3

[0057] The difference between this example and Example 1 is as follows:

[0058] (1) First aging treatment: The alloy sheet after the first cold rolling is kept at 325 °C for 8 h in a salt bath furnace and then cooled by water quenching.

[0059] (2) Second aging treatment: The alloy sheet after the second cold rolling is kept at 325 °C for 0.5 h in a salt bath furnace and then cooled by water quenching.

[0060] Example 4

[0061] The difference between this example and Example 1 is only that:

[0062] (1) Solution treatment: The alloy sheet after hot rolling is kept at 800 °C for 2 h and then quenched to room temperature in water.

[0063] Example 5

[0064] The difference between this example and Example 1 is only that:

[0065] (1) Pre-aging treatment: The alloy sheet after solution treatment is kept at 300 °C for 60 min in a salt bath furnace and then cooled by water quenching.

[0066] Example 6

[0067] The difference between this example and Example 1 is only that:

[0068] (1) Composition: Be: 1.5%, Ni: 0.6%, Co: 0%, Mg: 0.1%, the balance is Cu.

[0069] Example 7

[0070] The difference between this example and Example 1 is that:

[0071] (1) Composition: Be: 1.2%, Ni: 0.6%, Co: 0.2%, Mg: 0.1%, the balance is Cu.

[0072] (2) Hot rolling: After being kept at 870 °C for 2 h, hot rolling is carried out. The total hot rolling deformation is 85%, and it is rolled in three passes with deformation amounts of 35%, 30%, and 20% respectively.

[0073] (3) Solution treatment: The alloy sheet after hot rolling is kept at 880 °C for 2 h and then quenched to room temperature in water.

[0074] (4) First aging treatment: The alloy sheet after the first cold rolling is kept at 350 °C for 2 h in a salt bath furnace and then cooled by water quenching.

[0075] (5) Second aging treatment: The alloy sheet after the second cold rolling is kept at 350 °C for 2 h in a salt bath furnace and then cooled by water quenching.

[0076] Example 8

[0077] The differences between this embodiment and Embodiment 1 are as follows:

[0078] (1) Composition: Be: 0.8%, Ni: 0.7%, Co: 0.2%, Mg: 0.2%, and the balance is Cu.

[0079] (2) Solution treatment: After hot rolling, the alloy sheet is held at 900 °C for 1 h and then quenched in water to room temperature.

[0080] (4) First aging treatment: After the first cold rolling, the alloy sheet is held at 375 °C for 1 h in a salt bath furnace and then cooled in water.

[0081] (5) Second aging treatment: After the second cold rolling, the alloy sheet is held at 375 °C for 1 h in a salt bath furnace and then cooled in water.

[0082] Embodiment 9

[0083] The differences between this embodiment and Embodiment 1 are only as follows:

[0084] (1) Composition: Be: 1.4%, Ni: 0.2%, Co: 0.5%, Mg: 0.1%, and the balance is Cu.

[0085] (2) Hot rolling: After holding at 800 °C for 30 min, hot rolling is carried out. The total hot rolling deformation is 75%, and it is rolled in three passes with deformation amounts of 35%, 20%, and 20% respectively.

[0086] (3) Solution treatment: After hot rolling, the alloy sheet is held at 800 °C for 2 h and then quenched in water to room temperature.

[0087] Embodiment 10

[0088] The low-cost, high-strength, and high stress relaxation resistance Cu-Be-Ni-Co-Mg alloy and its preparation method in this embodiment are as follows:

[0089] Composition: Be: 1.1 wt%, Ni: 0.4 wt%, Co: 0.35 wt%, Mg: 0.15 wt%, and the balance is Cu.

[0090] The process flow is as follows:

[0091] (1) Melting: Electrolytic copper plates, Cu-Ni master alloy (Ni: 30%), Cu-Co master alloy (Co: 20%), beryllium copper master alloy (Be: 4%), and magnesium copper master alloy (Mg: 15%) are placed in a vacuum melting furnace. The vacuum is pumped to a vacuum degree ≤ 5×10 ﹣8 Pa, heated to 1250 °C for melting. After all the alloy raw materials are melted, the melt is poured into a water-cooled mold for cooling to obtain an alloy ingot.

[0092] (2) Homogenization treatment: The alloy ingot was subjected to homogenization treatment at 830 °C for 4 h under argon protection, and then water-cooled after the treatment was completed.

[0093] (4) Hot rolling: The homogenized alloy ingot was hot-rolled after holding at 820 °C for 1 h. The total hot-rolling deformation was 80%, and it was rolled in three passes with deformation amounts of 35%, 30%, and 15% of the total deformation amount respectively. After hot rolling, it was water-cooled to obtain alloy sheets.

[0094] (3) Solution treatment: The hot-rolled alloy sheets were quenched to room temperature after holding at 830 °C for 2 h.

[0095] (5) Pre-aging treatment: The solution-treated alloy sheets were held at 300 °C for 60 min in a salt bath furnace and then water-cooled.

[0096] (6) First cold rolling: The pre-aged alloy sheets were subjected to first cold rolling. The total cold rolling deformation was 80%, and it was divided into three passes with deformation amounts of 30%, 25%, and 20% of the total deformation amount respectively.

[0097] (7) First aging treatment: The alloy sheets after first cold rolling were held at 325 °C for 2 h in a salt bath furnace and then water-cooled.

[0098] (8) Second cold rolling: The alloy sheets after first aging treatment were subjected to second cold rolling. The total cold rolling deformation was 55%, and it was divided into two passes with deformation amounts of 35% and 20% respectively.

[0099] (9) Second aging treatment: The alloy sheets after second cold rolling were held at 315 °C for 1.5 h in a salt bath furnace and then water-cooled.

[0100] (10) Stress relief annealing treatment: The alloy sheets after second aging treatment were held at 200 °C for 1.5 h to obtain a low-cost, high-strength, and high stress relaxation resistance Cu-Be-Ni-Co-Mg alloy.

[0101] Comparative Example 1

[0102] Comparative Example 1 was a commercial QBe2.0 alloy with a composition of Be: 2 wt%, Ni: 0.3 wt%, Co: 0, Mg: 0, Al: 0.05%, and the balance being Cu.

[0103] The process flow is as follows:

[0104] (1) Melting: Electrolytic copper plates, Cu-Ni master alloy (Ni: 30%), and beryllium copper master alloy (Be: 3.5%) were used. The vacuum was pumped to a vacuum degree ≤ 5×10 ﹣8 Pa, and it was heated to 1250 °C for melting. After all the alloy raw materials were melted, the melt was poured into a water-cooled mold for cooling to obtain an alloy ingot.

[0105] (2) Homogenization treatment: The alloy ingot was subjected to homogenization treatment at 800 °C for 4 h, and argon gas was introduced for protection. After the treatment was completed, it was cooled by water quenching.

[0106] (3) Hot rolling: The alloy ingot after solution treatment was hot rolled after holding at 850 °C for 1 h. The total hot rolling deformation was 80%, and it was rolled in two passes with deformation amounts of 50%, 30%, and 15% of the total deformation amount respectively. After hot rolling, it was cooled by water quenching to obtain alloy sheets.

[0107] (4) Solution treatment: The alloy ingot after homogenization treatment was held at 800 °C for 30 min and then water quenched to room temperature.

[0108] (5) Cold rolling: The alloy sheets after pre-aging treatment were cold rolled once. The total cold rolling deformation was 60%, and it was divided into two passes with deformation amounts of 40% and 20% of the total deformation amount respectively.

[0109] (6) Aging treatment: The alloy sheets after one-time cold rolling were held at 325 °C for 2 h in a salt bath furnace and then cooled by water quenching.

[0110] Figure 2 For the scanning microstructure at the grain boundaries of the QBe2.0 alloy in Comparative Example 1, it can be seen from the figure that severe discontinuous precipitation occurred at the grain boundaries, forming discontinuous precipitation phases with a lamellar distribution, deteriorating the alloy properties. The alloy uses 2 wt% Be, and the cost is also higher than that of the example.

[0111] Comparative Example 2

[0112] The difference between Comparative Example 2 and Example 1 lies in the different alloy compositions. Its alloy composition is a commercial QBe2.0 alloy, that is, Be: 2 wt%, Ni: 0.3 wt%, Co: 0, Mg: 0, Al: 0.05%, and the balance is Cu.

[0113] Comparative Example 3

[0114] The difference between Comparative Example 3 and Example 1 is that the pre-aging process is removed.

[0115] Comparative Example 4

[0116] The difference between Comparative Example 4 and Example 1 is that the secondary cold rolling and secondary aging processes are removed.

[0117] The materials obtained from the examples and comparative examples were subjected to performance testing, as shown in Table 1:

[0118]

[0119] According to the performance data in Table 1, it can be seen that the Cu-Be-Ni-Co-Mg series alloy of the present invention has significant superiority in comprehensive performance compared with the traditional QBe2.0 alloy. First of all, through optimizing the composition design (adding elements such as Ni, Co, Mg, etc.) and the multi-stage aging process, the mechanical properties and electrical conductivity of the alloy are significantly improved. The addition of magnesium plays a key role: magnesium can not only dissolve in the copper matrix, refine the grain size, significantly improve the strength and toughness of the alloy, but also inhibit the formation of discontinuous precipitation phases (such as γ phase), promote the uniform distribution of precipitation phases, thereby improving the stress relaxation resistance and long-term service stability of the alloy;

[0120] Secondly, through the pre-aging process and the multi-stage aging process, the stress relaxation resistance of the alloy is significantly improved. Its stress relaxation rate at 200 °C / 1000 h is ≤8%, which is better than that of the traditional QBe2.0 alloy (the stress relaxation rate is generally 10% - 15%). In addition, by reducing the beryllium content (Be: 0.6% - 1.6%), the impact of beryllium on human health and the environment is reduced, and the safety and environmental protection of the material are improved. To sum up, this alloy is significantly superior to the traditional QBe2.0 alloy in terms of strength, hardness, stress relaxation resistance, electrical conductivity, elastic modulus, etc., and can better meet the stringent requirements for the comprehensive performance of materials in high-end fields such as aerospace precision relays, 5G high-frequency high-speed connectors, high-reliability defense electronic systems, and ultra-precision instruments and meters.

[0121] The above embodiments are merely examples clearly illustrating the present invention, rather than limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the embodiments here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy, characterized in that: The Cu-Be-Ni-Co-Mg series alloy has the following composition by mass percentage: Be: 0.6~1.6 wt%, Ni: 0~0.7 wt%, Co: 0~0.7 wt%, Mg: 0.05~0.5 wt%, where 0 < Ni + Co < 1 wt%, and the balance is Cu and unavoidable impurities.

2. The high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy according to claim 1, characterized in that: The Cu-Be-Ni-Co-Mg series alloy has the following composition by mass percentage: Be: 0.8~1.5 wt%, Ni: 0.1~0.7 wt%, Co: 0~0.5 wt%, Mg: 0.1~0.2 wt%, where Ni + Co < 1 wt%, and the balance is Cu and unavoidable impurities.

3. A high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy according to claim 1 or 2, characterized in that: The Cu-Be-Ni-Co-Mg series alloy has a tensile strength of 900~1400 MPa, an elastic modulus of 130~140 GPa, a conductivity of 25%~35% IACS, and a stress relaxation rate of ≤8% at 200 °C / 1000 h.

4. A method for preparing a high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy according to any one of claims 1 to 3, characterized in that: All components are proportionally taken and melted to obtain an alloy ingot. The alloy ingot is subjected to homogenization treatment to obtain a homogenized billet. The homogenized billet is subjected to hot rolling treatment to obtain a hot-rolled billet. The hot-rolled billet is subjected to solution treatment to obtain a solution-treated billet. The solution-treated billet is successively subjected to pre-aging, first cold rolling, first aging, second cold rolling, second aging, and stress relief annealing to obtain the final product.

5. The method for preparing a high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy according to claim 4, characterized in that: The smelting process is as follows: placing the electrolytic copper plate, the Cu-Ni master alloy, the Cu-Co master alloy, the beryllium copper master alloy and the magnesium copper master alloy in a vacuum smelting furnace, and evacuating the vacuum to a vacuum degree of ≤5×10 ﹣8 Pa, heating to 1080-1350°C for smelting, after all the alloy raw materials are melted, pouring the melt into a water-cooled mold for cooling, and obtaining an alloy ingot; The mass percentage of nickel in the Cu-Ni master alloy is 10%~45%, the mass percentage of cobalt in the Cu-Co master alloy is 10%~35%, the mass percentage of beryllium in the beryllium copper master alloy is 3%~6%, and the mass percentage of magnesium in the magnesium copper master alloy is 5%~25%.

6. The method for preparing a high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy according to claim 5, characterized in that: The homogenization treatment is carried out in a protective atmosphere. The temperature of the homogenization treatment is 800~950 °C, and the holding time is 4~8 h.

7. A method for preparing a high-strength and high stress-relaxation-resistant Cu-Be-Ni-Co-Mg series alloy according to claim 5, characterized in that: The temperature of the hot rolling is 850~900 °C. Before hot rolling, it is preheated at 850~900 °C for 1~3 h, and between passes, it is held at 850~900 °C for 15~30 min; The hot rolling is carried out in three passes. The total deformation amount of the hot rolling is 70~85%, and the deformation amounts of each pass are successively 35~40%, 20~35%, and 15~30% of the total deformation amount; The temperature of the solution treatment is 780~950 °C, and the holding time is 15 min~4 h. After the solution treatment is completed, it is quenched in water to room temperature.

8. The method for preparing a high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy according to claim 5, characterized in that: The pre-aging treatment is carried out in a salt bath. The temperature of the pre-aging treatment is 280~320 °C, and the holding time is 5~60 min.

9. The method for preparing a high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy according to claim 5, characterized in that: The first cold rolling is carried out in three passes. The total deformation amount of the first cold rolling is 70~80%, and the deformation amounts of each pass are successively 30~35%, 20~30%, and 15~20% of the total deformation amount; The first aging is carried out in a salt bath. The temperature of the first aging is 325~450 °C, and the holding time is 1~8 h; The secondary cold rolling is performed in two passes, the total deformation of the secondary cold rolling is 50-60%, and the deformation of each pass is 30-40% and 20-30% of the total deformation respectively; The secondary aging is carried out in a salt bath, the temperature of the secondary aging is 300-400° C., which is lower than the temperature of the primary aging, and the insulation time is 0.5-3 hours.

10. The method for preparing a high-strength and high-stress relaxation-resistant Cu-Be-Ni-Co-Mg alloy according to claim 5, characterized in that: The stress relief annealing temperature is 180-300° C., and the insulation time is 1-2 hours.

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