High temperature mechanical behavior of alumina dispersion strengthened copper alloy with high content of alumina

Abstract

The microstructure and its effects on the high temperature mechanical behavior of Cu–2.7%Al2O3 (volume fraction) dispersion strengthened copper (ADSC) alloy were investigated. The results indicate that fine alumina particles are uniformly distributed in the copper matrix, while a few coarse ones are distributed on the grain boundaries. Tensile tests results show that Hall-Petch mechanism is the main contribution to the yield strength of ADSC alloy at room temperature. Its high temperature strength is attributed to the strong pinning effects of alumina particles on the grain and sub-grain boundaries with dislocations. The ultimate tensile strength can reach 237 MPa and the corresponding yield strength reaches 226 MPa at 700 °C. Tensile fracture morphology indicates that the ADSC alloy shows brittleness at elevated temperatures. Creep tests results demonstrate that the steady state creep rates at 400 °C are lower than those at 700 °C. The stress exponents at 400 °C and 700 °C are 7 and 5, respectively, and the creep strain rates of the ADSC alloy are controlled by dislocation core diffusion and lattice diffusion.