Properties of Cu-Al2O3 Powder and Compact Composites of Various Starting Particle Size Obtained by High-Energy Milling

Abstract

Copper-based composites were obtained using high energy milling. The inert gas-atomized prealloyed copper powder (average particle size - 30 μm) containing 2 wt.% Al, and the mixture of electrolytic copper powder (average particle size – 30 and 15 μm) with 4 wt.% comertial Al2O3 powders (average particle size –0.75μm) served as starting materials. These powders were separately milled in air up to 20 h in the planetary ball mill. Milling of prealloyed copper powder promotes formation of nano-sized Al2O3 particles by internal oxidation with oxygen from air. It was calculated that by internal oxidation of 2 wt.% aluminum approximately 3.7 wt.% Al2O3 was generated in the copper matrix. Milled powders were treated in hydrogen at 400 °C for 1 h in order to eliminate copper oxides formed at the surface during milling. Compaction executed by hot-pressing was carried out in an argon atmosphere at 800 °C for 1 h under the pressure of 35 MPa. Compacts obtained from 5 and 20 h milled powders were additionally subjected to high-temperature exposure in argon at 800 °C for 1 and 5 h. The results were discussed in terms of the effects of different size of starting powder particles on structure, strengthening of copper matrix, thermal stability and electrical conductivity of the Cu - Al2O3 composite.