Microstructure and properties of Cu-Cr-Zr (Mg) alloys subjected to cryorolling and aging treatment

Abstract

In this study, the Cu-1Cr-0.2Zr (wt%) alloys with trace Mg element (0.05 wt%) were prepared by a two-step cryorolling and aging (CRA) process. The effects of the two-step CRA and Mg element on the microstructural evolution, mechanical properties, and electrical conductivity were investigated. High-density deformation twins and dislocations were observed in the Cu-Cr-Zr-Mg alloys subjected to the two-step CRA process. Compared with the Cu-Cr-Zr alloys subjected to two-step room temperature rolling (RTRA), the widths of deformation bands and twins of the two-step CRA Cu-Cr-Zr-Mg alloys decreased by 11.5% and 34%, respectively. The high-density dislocations in the two-step CRA Cu-Cr-Zr-Mg alloys provided more nucleation sites for the precipitates during the subsequent aging process. Despite within the subgrains and twins, fine precipitates in the two-step CRA Cu-Cr-Zr-Mg alloys were also observed at the grain boundaries and twin boundaries. The fine precipitates (∼5.9 nm) pinned the motion of dislocations, enhancing the performance of Cu-Cr-Zr-Mg alloys effectively. The high electrical conductivity was ascribed to the depletion of the Cr and Zr elements from copper matrix after the aging process. With the synergistic effect of the Mg element and the two-step CRA process, the high tensile strength of 629 MPa and electrical conductivity of 79.66% IACS (International Annealed Copper Standard) were simultaneously achieved in this study.