Mechanical Properties of Cu–Ag Microcomposites Thermo-Mechanically Processed by Equal Channel Angular Pressing (ECAP)

Abstract

Equal channel angular pressing (ECAP) combined with intermediate heat treatment was carried out on Cu-15 wt.% Ag at room temperature. ECAPed Cu-15 wt. Ag exhibited ultrafine structure with the shape and distribution of Ag phase dependent on the processing routes. The initial lamellae of Ag phase were elongated along the shear direction and developed into filaments in route A whereas the initial lamellae became finer by fragmentation with no pronounced change of the shape in route Bc. The application of intermediate heat treatment at 330 � C was found to increase the hardness greatly for all three different routes. The network lamella structure usually observed in route C without intermediate heat treatment was not well developed in the specimen with one intermediate heat treatment. The dissolution Ag lamellae with high strain energy and re-precipitation of Ag precipitates is thought to be responsible for the irreversible slip in route C since Ag precipitates in the matrix are likely to act as obstacles to the reversible slip of dislocations, leading to the easier modification of thin-walled network-like structure. The presence of more precipitates in Cu-15 wt.Ag specimens ECAPed with intermediate heat treatment supports the effect of Ag precipitation on the microstructure and the hardness.