Development of a magnesium-alumina composite through cold consolidation of machining chips by high-pressure torsion

Abstract High pressure torsion offers unique conditions for the consolidation of metallic particles at room temperature owing to the high hydrostatic compressive stresses combined with the high shear strain. A Mg-Al 2 O 3 composite was produced by consolidation of machining chips of pure magnesium with 10% in volume of alumina particles. The consolidation process was investigated by optical and scanning electron microscopy and X-ray microtomography. It is shown that shear deformation concentrates along thick alumina particle layers in the initial stage of deformation. A significant fraction of the hard phase particles are pushed into the outflow in quasi-constrained HPT and a homogeneous composite is achieved after significant straining. The composite exhibits a refined microstructure, a higher hardness and improved resistance against room temperature creep compared to pure magnesium.