A Study On Microstructures And High-temperature Mechanical Properties Of Cu-Al₂O₃Dispersion Strengthened Copper

In this paper, The microstructures and high-temperature mechanical properties were studied by the means of optical microscopy, scanning electron microscopy, transmission electron microscopy, XRD, hardness tests, high temperature tensile and creep tests. The conclusions were as follows:(1) When the Al content was relatively low (0.05wt.%Al), the major oxidation products were γ=Al2O3in Cu-Al2O3dispersion strengthened copper(ADSC) alloy, these y-Al2O3particles dispersed uniformly in the copper matrix. When the Al content was relatively high (0.6wt.%Al), the first generated y-A12O3particles then aggregated, grew up and coarsened, transformed into a more stable phase. The oxidation products contained a, y,9etc. The transitions among different phases of A12O3particles were related to the temperature, the phase transition only occurred above1100℃, and final converted into a-Al2O3.(2) The room temperature tensile strength of Cu-Al2O3dispersion strengthened copper(ADSC) alloy reached560MPa, and the tensile strength and yield strength at700℃were237MPa and226MPa respectively. The strengthening effects of ADSC alloy at room temperature were mainly due to Hall-Petch mechanism and the interaction of moving dislocation and dispersion distributed alumina particles. The room temperature tensile fracture type is ductile, and the high-temperature fracture modes were mixed, plasticity reduced with the increasing temperature.(3) The effect of strengthening of Cu-2.7vol.%Al2O3ADSC alloy was rather dramatic compared with the pure copper, the creep strain rate at400℃and700℃were controlled by the lattice diffusion and the dislocation core diffusion respectively, and the stress exponent were close to7and5.