Microstructure and properties of rare earth-containing Cu–Cr–Zr alloy

Cu–0.81Cr–0.12Zr–0.05La–0.05Y (mass fraction) alloy was successively subjected to hot rolling, solid solution treatment, cold rolling and aging treatments. Its microstructure, microhardness and electrical conductivity at different states were systematically investigated. The as-cast microstructure consists of three phases: Cu matrix, Cr and Cu5Zr. Zr is completely dissolved into the matrix while partial Cr remains after the solid solution treatment. Aging of the cold-rolled sample makes nanocrystals of Cr and Cu5Zr precipitate from the matrix, and the microhardness and electrical conductivity rise. A combination of high microhardness (HV 186) and high conductivity (81% IACS) can be obtained by aging the sample at 773 K for 60 min. As the aging temperature increases, the orientation degree of the Cu crystals gradually decreases to zero, but the microstrain in them cannot be eliminated completely owing to the presence of precipitates and dislocations. The Cr precipitates exhibit the N–W orientation relationship with the matrix when the coherence strengthening mechanism plays a main role.