Effect of cryogenic rolling and multistage thermo-mechanical treatment on the microstructure and properties of the Cu-0.4Cr-0.39Zn-0.1Mg-0.07Zr alloy

Abstract

A Cu-0.4Cr-0.39Zn-0.1Mg-0.07Zr (wt%) alloy was prepared using cryogenic rolling process and multistage thermo-mechanical treatment to achieve excellent comprehensive properties with tensile strength of 635 MPa, yield strength of 620 MPa and electrical conductivity of 75.3% IACS. A large number of nano deformation twins appeared in the alloy after cryogenic rolling, and the width of the nano twins decreased with the deformation, and the average width of nano twins decreased by 8.4% and 11.8% after the second and the third cryogenic rolling, respectively. The high density of dislocations introduced by cryogenic rolling provided more nucleation sites for Cr phase precipitation, which promoted the diffusive precipitation of Cr phase. With the synergy of microalloying of Mg and Zn elements, cryogenic rolling and multistage thermo-mechanical treatment, the copper alloy with high density of nano deformed twins, fine and diffuse precipitation phases and excellent performance was prepared, which can be used as high-performance copper alloys for lead frames of large-scale integrated circuits.