Microstructure and mechanical properties of near net shaped aluminium/alumina nanocomposites fabricated by powder metallurgy

Abstract Near net shaped metal matrix composites were fabricated using high energy cube milling and hot pressing process. Cube milling was up to six times faster than commercially available planetary ball mill in dispersing up to 1 vol.% of Al 2 O 3 nanoparticles in AlMg5 alloy. Combined yield strength of 530 MPa and elongation at rupture of 4% exceed the values of commercially available wrought 5xxx series alloys. Thorough microstructure characterisation of composites revealed bimodal grain structure with an increasing content of finer grains and high angle grain boundaries with higher reinforcement content. The main contributing strengthening mechanisms for achieving high strength were solid solution strengthening, Orowan strengthening and grain boundary strengthening. Coarse grained regions in the bimodal structure, together with low angle grain boundaries were assumed to be the main source of retained ductility.