Research On Composition Design,Microstructure And Properties Of High Strength And High Conductivity Cu-Zn-Cr-Zr Alloy Performance

Cu-Cr-Zr alloy is a typical precipitation strengthening copper alloy that is widely used in advanced fields such as lead frames for large-scale integrated circuits,contact wires for high-speed rail transit systems,aerospace and aviation connectors,and terminal blocks for new energy vehicles.With the rapid development of the electronic information industry,there are increasing demands for the strength and conductivity of copper alloys.The traditional Cu-Cr-Zr alloy has a strength range of 500-650 MPa and a conductivity of 65-85%IACS.The development of Cu-Cr-Zr alloys with higher strength and conductivity has become a hot research topic.However,there is a contradiction between strength and conductivity.Therefore,this article focuses on the effects of alloying,processing,and deformation heat treatment on the microstructure and properties of Cu-Zn-Cr-Zr alloys by adding inexpensive Zn elements to Cu-Cr-Zr alloy.Through composition design and optimization of deformation heat treatment processes,a high-performance copper alloy with a tensile strength of≥700 MPa and a conductivity of≥70%IACS(hereinafter referred to as the "dual-70" alloy)is developed.The main aspects are as follows:(1)By adding alloying elements such as Cr,Zr,and Zn to the copper alloy,a Cu0.4Zn-0.35Cr-0.2Zr alloy was designed.The optimal thermo-mechanical treatment process is solid solution+70%cold rolling+400□/1h aging+50%cold rolling+400□/5h aging+70%cold rolling+350□/15min stress relief annealing.The prepared alloy has a tensile strength of 672 MPa,a yield strength of 670 MPa,and an electrical conductivity of 72.1%IACS.(2)By optimizing the alloy composition,a Cu-0.72Zn-0.6Cr-0.2Zr alloy was designed,and the thermo-mechanical treatment process was optimized,i.e.,solid solution+420□/1h pre-aging+70%cold rolling+420□/1h aging+70%cold rolling+420□/3h aging+50%cold rolling+350□/60min stress relief annealing.The prepared alloy has a tensile strength of 702 MPa,a yield strength of 695 MPa,and an electrical conductivity of 71.3%IACS,developing a "double 70" high-strength and high-conductivity Cu-Zn-Cr-Zr alloy.(3)The added Zn element is uniformly dissolved in the copper matrix.The addition of an appropriate amount of Zn element not only improves the process performance of the alloy but also increases the strength of the alloy without significantly reducing the electrical conductivity when combined with the proper thermo-mechanical treatment process.(4)During the aging process,a large amount of Cr and Zr elements precipitate from the matrix.The precipitated phases in the alloy mainly exist in the form of nanoscale Cr phases,with a size of about 5 nm,and most of the Cr phases maintain a high degree of coherency with the matrix in a cube-on-cube relationship.As the aging time increases,precipitated phases with N-W and K-S relationships appear,and the Cr phases transform from FCC structure to BCC structure.The precipitation sequence of Cr phases is:G.P.zone(FCC structure)→coherent or non-coherent(FCC structure)→K-S relationship(BCC structure).(5)Compared with the Cu-0.4Zn-0.35Cr-0.2Zr alloy,increasing the content of Zn and Cr elements in the Cu-0.72Zn-0.6Cr-0.2Zr alloy results in more Cr phases,higher dislocation density,and stacking faults,thereby enhancing the interaction between the Cr phases and dislocations,and ultimately improving the strength of the alloy.(6)Through the calculation and analysis of classical strength theory,the contribution of different strengthening effects in Cu-Zn-Cr-Zr alloys is in the order of dislocation strengthening,precipitation strengthening,grain refinement strengthening,and solid solution strengthening.