Correlation between microstructure and mechanical properties in the age-hardenable Cu-Cr-Zr alloy

Cu-Cr-Zr alloy, a copper-based precipitation hardened alloy with good electrical and thermal conductivities and moderate strength at elevated temperatures, is being considered for many advance technological applications including fusion energy programme. Ageing study on indigenously manufactured Cu-Cr-Zr alloy (0.7-0.8 wt.% Cr, 0.08-0.11wt.% Zr, balance Cu) has been performed in the temperature range of 673 K – 773 K and time from 30 min to 5 h to find the peak ageing conditions for this alloy. The peak ageing conditions were achieved at 3 h of heat-treatment at 723 K. An attempt has been made to identify the precipitates using analytical transmission electron microscopy and to classify them based on morphology, sizes and distribution. Besides the larger precipitates of Cu₅CrZr, two clearly distinct sizes of smaller precipitates were observed. Electron microscopy revealed that the larger precipitates are having spherical and cuboidal morphology. The temperature dependent flow behavior of Cu-Cr-Zr alloy in peak aged condition was evaluated in the range of 298 K to 1073 K in 100 K interval. The dislocation arrangement and the dislocation precipitate interaction were examined to understand the contribution of the precipitates in strengthening and also in work hardening behavior of the alloy.