The effect of reinforcement content and milling time on microstructure and mechanical properties of Al–10Mg/xAl2O3 nanocomposites

The microstructural changes and mechanical properties of Al–10 wt% Mg/xAl2O3 (x=0, 5, 10 and 15 wt%) nanocomposites during milling were investigated. The structural evolution of the Al–10Mg/Al2O3 powders during mechanical milling, due to the presence of alumina particles, occurred faster than that of the non-reinforced Al–10Mg powder. For the binary Al–Mg matrix, the acceleration of the grain refinement process (to 25 nm) was observed due to generation of dislocations by the addition of reinforcement particles. For non-reinforced Al–10Mg sample with up to 10 h, microhardness increases to 129 HV due to solid solution hardening and dislocation density as well as the decrease of the crystallite size. The acceleration of the grain refinement process by adding alumina particles leads to increase in microhardness (about 175 HV for 15 wt% Al2O3). From 10 to 20 h, slower rate of increasing in microhardness may be attributed to the completion of alloying process, and dynamic and static recovery of powders.