Deformation microstructures, strengthening mechanisms, and electrical conductivity in a Cu–Cr–Zr alloy

The ultrafine-grained microstructures, mechanical properties and electrical conductivity of a Cu–0.87%Cr–0.06%Zr alloy subjected to multiple equal channel angular pressing (ECAP) at temperatures of 473–673K were investigated. The new ultrafine grains resulted from progressive increase in the misorientations of strain-induced low-angle boundaries during the multiple ECAP process. The development of ultrafine-grained microstructures is considered as a type of continuous dynamic recrystallization. The multiple ECAP process resulted in substantial strengthening of the alloy. The yield strength increased from 215MPa in the original peak aged condition to 480MPa and 535MPa after eight ECAP passes at 673K and 473K, respectively. The strengthening was attributed to the grain refinement and high dislocation densities evolved by large strain deformation. Modified Hall–Petch analysis indicated that the contribution of dislocation strengthening to the overall increment of yield stress (YS) through ECAP was higher than that of grain size strengthening. The formation of ultrafine grains containing high dislocation density leads to a small reduction in electrical conductivity from 80 to 70% IACS.