Microstructure and strengthening mechanisms of CuCrZr alloy by two-step thermomechanical treatment

Abstract

The high strength obtained in Cu–Cr alloys is mainly attributed to the precipitation strengthening, dislocation strengthening, and grain-boundary strengthening. The precipitate size, dislocation density, and grain size are related to thermomechanical treatment. The strength of Cu–Cr alloys can be controlled by the thermomechanical treatment process. In this study, the microstructure and strengthening mechanisms of Cu–0.8Cr–0.1Zr (wt%) alloy after one-step and two-step thermomechanical treatment were studied. The results showed that after the following thermomechanical treatments, solution treated at 950 °C for 60 min, thickness reduction at first cold rolled for 60%, annealed at 450 °C for 180 min, and then 30% thickness reduction in secondary cold rolling, the microhardness, tensile strength, and conductivity reach 215 HV, 623 MPa, and 74.5% IACS, respectively. The main difference of strength between one-step and two-step thermomechanical treatment in the Cu–0.8Cr–0.1Zr alloy is due to the difference of dislocation strengthening effect. The dislocation strengthening achieved in two-step thermomechanical treatment (175.6 MPa) is 95 MPa greater than that of one-step thermomechanical treatment (80.6 MPa).