Properties of copper matrix reinforced with various size and amount Of Al2O3 particles
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Copper matrix was reinforced with Al2O3 particles of different size and amount by internal oxidation and mechanical alloying accomplished using high-energy ball milling in air. The inert gas-atomised prealloyed copper powder containing 1 wt.% Al as well as a mixture of electrolytic copper powder and 3 wt.% commercial Al2O3 powder served as starting materials. Milling of Cu-1 wt.% Al prealloyed powder promoted formation of fine dispersed particles (1.9 wt.% Al2O3, approximately 100 nm in size) by internal oxidation. During milling of Cu-3 wt.% Al2O3 powder mixture the uniform distribution of commercial Al2O3 particles has been obtained. Following milling, powders were treated in hydrogen at 400 degrees C for 1 h in order to eliminate copper oxides formed at the surface during milling. Compaction was executed by hot-pressing. Compacts processed from 5 to 20 h-milled powders were additionally subjected to high-temperature exposure at 800 degrees C in order to examine their thermal stabili...ty and electrical conductivity. Compacts of Cu-1 wt.% Al prealloyed powders with finer Al2O3 particles and smaller grain size exhibited higher microhardness than compacts of Cu-3 wt.% Al2O3 powder mixture. This indicates that nano-sized A1203 particles act as a stronger reinforcing parameter of the copper matrix than micro-sized commercial Al2O3 particles. Improved thermal stability of Cu-1 wt.% Al compacts compared to Cu-3 wt.% Al2O3 Compacts implies that nano-sized Al2O3 particles act more efficiently as barriers obstructing grain growth than micro-sized particles. Contrary, the lower electrical conductivity of Cu-1 wt.% Al compacts is the result of higher electron scatter caused by nano-sized Al2O3 particles. (c) 2007 Elsevier B.V. All rights reserved.