Abstract
Inert gas atomized prealloyed copper powder containing 2 wt.% Al (average particle size ? 30 ?m) and a mixture consisting of copper (average particle sizes ? 15 ?m and 30 ?m) and 4 wt.% of commercial Al2O3 powder particles (average particle size ? 0.75 ?m) 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 Al2O3 particles. Milling in air of prealloyed copper powder promoted formation of finely dispersed nano-sized Al2O3 particles by internal oxidation. On the other side, composite powders with commercial micro-sized Al2O3 particles were obtained by mechanical alloying. Following milling, powders were treated in hydrogen at 400 0C for 1h in order to eliminate copper oxides formed on their surface during milling. Hot-pressing (800 0C 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 5h 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 Al2O3 particles on strengthening, thermal stability and electrical conductivity of copper-based composites.
Highlights
IntroductionCopper-based composites with a fine dispersion of Al2O3 particles produced by highenergy milling have been extensively studied in recent years [1,2,3] due to attained better properties than for pure copper and precipitation or solid solution hardened copper
The results were discussed in terms of the effects of different size of starting powders, the grain size refinement and different size of Al2O3 particles on strengthening, thermal stability and electrical conductivity of copper-based composites
Copper-based composites with a fine dispersion of Al2O3 particles produced by highenergy milling have been extensively studied in recent years [1,2,3] due to attained better properties than for pure copper and precipitation or solid solution hardened copper
Summary
Copper-based composites with a fine dispersion of Al2O3 particles produced by highenergy milling have been extensively studied in recent years [1,2,3] due to attained better properties than for pure copper and precipitation or solid solution hardened copper. High-energy milled powders are distinguished by a very fine, nano-scaled grain structure, which may be retained even during compaction. This fine-grained structure contributes to copper matrix strengthening together with Al2O3 particles. Dispersion strengthened Cu- Al2O3 composite materials are extensively used as materials for products, which require high-strength and electrical properties, such as electrode. Electrode tips made of this composite material which operating temperature is approximately 800oC demonstrate much higher softening (recrystalization) temperature than tips made of standard high strength and high conductivity copper alloys [4]. The main requirement for structure of dispersion-strengthened materials is a homogenous distribution and small size of oxide particles. The effect of the various size of copper and Al2O3 powder particles on strengthening, thermal stability and electrical conductivity of Cu - Al2O3 composites obtained by hot-pressing was the object of this paper
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