Effect of Heat Treatment on the Microstrucre of Cu-Cr-Zr Allou

摘要

Effect of Heat treatments on microstructure in a Cu-0.71Cr-0.12Zr alloy (in wt.%) have been investigated. The microstructures are analyzed by optical microscope, scanning electron microscope, transmission electron microscope and high-resolution transmission electron microscope after each step of heat treatments. The results show that the as-cast microstructure of Cu-Cr-Zr alloy is Cu matrix, Cr dendrite and eutectic structure which is composed of Cu and Cu_5Zr phase with a fine lamellar structure. By increasing the homogenization temperature or prolonging the holding time, the eutectic structure is dissolved into the matrix gradually and the volume fraction of the Cr phases is obviously reduced. The precipitation of Cr phase prevents from Zr-rich phases dissolving in the matrix. And the proper homogenizing process is 900°C×l2 h. When the alloy aged at 450°C for 24 h, the crystallography of Cr precipitates and the orientation relationship between Cr precipitates and Cu matrix is bcc structure and KS-OR, respectively. The disk-shaped precipitate is identified as Cu_5Zr phase and their habit plane is parallel to {111 }cu plane.