The Influence of Powder Particle Size on Properties of Cu-Al_2O_3 Composites

摘要

Inert gas atomized prealloyed copper powder containing 2 wt.%Al (average particle size ≈ 30 ym) and a mixture consisting of copper (average particle sizes ≈ 15 μm and 30 μm) and 4 wt. % of commercial Al_2O_3 powder particles (average particle size ≈ 0.75 μm) were milled separately in a high-energy planetary ball mill up to 20 h in air. Milling was performed in order to strengthen the copper matrix by grain size refinement and Al_2O_3 particles. Milling in air of prealloyed copper powder promoted formation of finely dispersed nano-sized Al_2O_3 particles by internal oxidation. On the other side, composite powders with commercial micro-sized Al_2O_3 particles were obtained by mechanical alloying. Following milling, powders were treated in hydrogen at 400 °C for 1h in order to eliminate copper oxides formed on their surface during milling. Hot-pressing (800 °C for 3 h in argon at pressure of 35 MPa) was used for compaction of milled powders. Hot-pressed composite compacts processed from 5 and 20 h milled powders were additionally subjected to high temperature exposure (800 °C for 1 and 5 h in argon) in order to examine their thermal stability. The results were discussed in terms of the effects of different size of starting powders, the grain size refinement and different size of Al_2O_3 particles on strengthening, thermal stability and electrical conductivity of copper-based composites.