Internal oxidation of Cr in Cu–Cr/Cu2O composite powder prepared by mechanical activation

The preparation of Cr2O3/Cu composite is discussed using mechanical activation to promote the internal oxidation of Cr during sintering of CuCr/Cu2O powder. Experiments were carried out to evaluate the processing parameters during the preparation. Temperature for a sufficient oxidation of Cr was in the temperature range of 1176–1325 K. The maximum oxygen partial pressure increased with increasing temperature in these experiments. It is shown that the mechanical activation can promote diffusion and reaction efficiently. 0.22 h is regarded as the minimum time for the internal oxidation in this process. Since the exothermic effect is huge during the internal oxidation of Cr, the heating rate and the reaction temperature must be chosen very carefully depending on Cr content. Spherical grains of Cr2O3 with a size of 2–5 μm in diameter were observed uniformly dispersed in Cu matrix and the distance between the particles was about 5–10 μm. The properties of the Cr2O3/Cu composite can be further improved by heat treatment. Therefore, mechanical activation and using Cr instead of Al in a Cr2O3/Cu composite is recommended to make the internal oxidation easier to control.