Achieving high strength and high electrical conductivity Cu–Cr–Zr alloys by continuous extrusion and thermomechanical treatment
Fangxu Qi, Hongwang Fu, Xinbing Yun
Abstract
A high strength and high electrical conductivity Cu–Cr–Zr alloy was obtained by continuous extrusion and thermomechanical treatment . Without solution treatment of the raw material, the combined process can promote the microhardness , tensile stress , and electrical conductivity to 200.4 HV0.3, 607 MPa, and 79.3 % IACS, respectively. The excellent comprehensive properties were obtained from systematically performed experiments. It was found that direct aging of as-cast or extruded alloy can not enhance the mechanical strength significantly compared with that of the extruded-rolled alloy, implying that the dislocation density plays a crucial role in the precipitation process. Cold rolling with a reduction rate of 80 % can enhance the dislocation density dramatically, promoting the precipitation process at the aging temperature of 400 °C. Then, the contribution of the precipitation strengthening mechanism on the total yield stress increases from 16.4 % in the extruded state to 26.4 % in the extruded-rolled-aged state. The precipitation sequence during the process was characterized as mainly meta-stable f.c.c. Cr after extrusion to stable b.c.c. Cr and Cu 4 Zr after thermomechanical treatment. The orientation relationship between the Cu matrix and Cu 4 Zr precipitates is: [ 011 ] Cu //[ 100 ] Cu4Zr , ( 0 2 ‾ 2 ) Cu //( 040 ) Cu4Zr . The investigation provides new insights into manufacturing high-performance Cu–Cr–Zr strips.