Effect of different solid solution treatments on microstructure and properties of Cu-Cr alloy

Heat treatment is well-known to be effective to improve the performance of Cu-Cr alloys. The solid solution process of Cu-Cr alloys mostly selects the lower temperature Cu-Cr two-phase region, resulting in incomplete dissolution of Cr phase and inhibiting subsequent precipitation strengthening effect. A high-temperature single-phase region solid solution process was proposed to improve the strengthening effect. The effects of different solid solution processes ((950 ℃, 4 h) in the two-phase region and (1050 ℃, 6 h) in the single-phase region) on the microstructure and properties of Cu-Cr alloy were comparably studied. The element distribution after two solid solution processes was characterized by electron probe microanalyzer (EPMA), and the microstructure of the peak-aged alloy was characterized and analyzed by XRD and TEM. The results show that, compared with solid solution in the two-phase region, the cast Cr phase is fully dissolved after solid solution in the single-phase region, and more nano Cr phases precipitate during aging. The mechanical properties of the alloy are significantly improved compared to those of the alloy at the peak-aged state after solid solution in the two-phase region, the yield strength increases by 29.3% and tensile strength increases by 25.6%, while the electrical conductivity does not decrease significantly. Strength theory calculations results indicate that the yield strength increment contributed by precipitation strengthening is 323.4 MPa, accounting for 56.9%, which is the most significant strengthening mechanism in this study. © 2024 Central South University of Technology. All rights reserved.