| With the continuous development of modern science and technology and the electronic information industry,the application of copper and copper alloys has become more and more extensive,but the performance requirements of copper alloys have become more and more demanding.As a typical age-strengthened copper alloy,Cu-Cr alloy has excellent properties and has been widely used in industry.Adding alloy elements to further improve the performance of Cu-Cr alloys has been a research focus,but mainly focused on Cu-Cr-Zr alloys.Sn and Zn elements have little effect on the conductivity of copper alloy and can improve it’s strength.For this reason,Cu-0.67Cr-0.23Sn、Cu-1.0Cr-0.18Sn and Cu-0.77Cr-0.22Sn0.37Zn are designed in this paper.The microstructure,mechanical properties and electrical properties of the three alloys with solid solution state,cold rolling state and aged state were studied by means of microhardness test,tensile test at room temperature,electrical conductivity test and microstructure analysis(OM,SEM and TEM).In addition,based on the conductivity of the three alloys aged at 400℃ with different times,the precipitation kinetics of the three alloys at 400℃ was studied.The main results are as follows:(1)The microstructure and properties of Cu-0.67Cr-0.23Sn,Cu-1.0Cr-0.18Sn and Cu0.77Cr-0.22Sn-0.37Zn alloys with solid solution state were studied.The results show that the strengthening effect on the copper alloy after adding the solid solution element is limited,but the conductivity is seriously reduced.The tensile strengths of Cu-0.67Cr-0.23Sn,Cu-1.0Cr0.18Sn and Cu-0.77Cr-0.22Sn-0.37Zn alloy after solution treatment was 246.54MPa,254.25MPa and 246.71MPa,and the electrical conductivity was 48.58%IACS,47.57%IACS,and 45.28%IACS respectively.(2)The microstructure and properties of Cu-0.67Cr-0.23Sn,Cu-1.0Cr-0.18Sn and Cu0.77Cr-0.22Sn-0.37Zn alloys with cold rolling state were studied.The results show that the cold deformation can greatly improve the mechanical properties of the three alloys,and the loss of conductivity is not serious.For Cu-0.67Cr-0.23Sn alloy,the tensile strength increased by 223.63MPa and the electrical conductivity decreased by only 1.98%IACS after it was rolled by 90%.(3)The microstructure and properties of Cu-0.67Cr-0.23Sn,Cu-1.0Cr-0.18Sn and Cu0.77Cr-0.22Sn-0.37Zn alloys with aged state were studied.The results show that the improvement of mechanical properties and electrical properties of the three alloys are not obvious after aged at 350℃ for different time.The electrical conductivity of the three alloys increases rapidly after aged at 400℃and 450℃,but the microhardness and strength decrease with the increase of the aging time.A good match between mechanical and electrical properties of the three alloys can be obtained after aged for different times at 400℃ and 450℃.For the Cu-0.67Cr-0.23Sn with 90%cold rolling reduction,the single stage aging system with the best comprehensive performance is aging at 400℃ for 1.5h,and the tensile strength and electrical conductivity reach 507.17 MPa and 73.58%IACS respectively.The of Cu-1.0Cr-0.18Sn and Cu-0.77Cr-0.22Sn-0.37Zn alloys with 90%cold rolling reduction all obtained the best comprehensive performance at 400℃ aging for 2h,with the tensile strength of 505.62MPa and 523.14MPa,and the electrical conductivity of 72.43%IACS and 69.20%IACS,respectively.(4)The Cu-0.67Cr-0.23Sn and Cu-1.0Cr-0.18SnCr alloys are solution treated at a temperature lower than 1076℃.Since the Cr element with exceeds the ultimate solid solubility forms Cr-rich second phase on the matrix,the properties of the two alloys show little difference.(5)Based on the electrical conductivity of the three Cu-Cr-Sn alloys aged at 400℃ for different time,the Avrami phase transformation kinetics equation was used to describe the aging process of the three Cu-Cr-Sn alloys at this temperature.The conductivity equation of the three alloys aging at 400℃was deduced,and the error between the calculated value and the measured value was within 4%. |
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