Effects of copper and Al2O3 particles on characteristics of Cu-Al2O3 composites

High-energy milling was used for production of Cu-Al2O3 composites. The inert gas-atomized prealloyed copper powder containing 2 wt.%Al and the mixture of the different sized electrolytic copper powders with 4 wt.% commercial Al2O3 powders served as starting materials. Milling of prealloyed copper powders promotes formation of nano-sized Al2O3 particles by internal oxidation with oxygen from air. Hot-pressed compacts of composites obtained from 5 and 20 h milled powders were additionally subjected to the high-temperature exposure in argon at 800 oC for 1 and 5 h. Characterization of processed material was performed by optical and scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), microhardness, as well as density and electrical conductivity measurements. Due to nano-sized Al2O3 particles microhardness and thermal stability of composite processed from milled prealloyed powders are higher than corresponding properties of composites processed from the milled powder mixtures. The results were discussed in terms of the effects of different size of starting copper powders and Al2O3 particles on the structure, strengthening of copper matrix, thermal stability and electrical conductivity of Cu-Al2O3 composites.