Mechanical induced reaction in Al-CuO system for in-situ fabrication of Al based nanocomposites

Gradual chemical (displacement) reaction between CuO and Al powders during high-energy attrition milling under a high purity argon atmosphere was studied. Differential thermal analysis (DTA), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were employed to study the solid-state reaction. It was shown that the solid-state reaction occurred during mechanical alloying (MA) and resulted in the dissolution of copper into the aluminum lattice and formation of nanometric alumina particles. The reinforcement particles were mostly distributed at the grain boundaries of Al matrix with an average crystallite size of about 50 nm. In DTA curve of the milled powders, a small exothermic peak after Al melting was noticed. The peak became smaller, i.e. less exothermic, with increasing the milling time, indicating that the solid-state reaction occurs gradually during MA. While the oxide particles formed by MA were found to be nanometric with almost uniform size distribution, the reaction product of Al melt and CuO was clustered and ultrafine. This observation indicated the advantage of mechanically induced solid-state reaction (mechanical alloying) over liquid-solid reaction (casting) for in-situ processing of metal matrix nanocomposites.