Enhanced mechanical properties and near unity yield asymmetry in equiatomic high entropy alloy particles reinforced magnesium composites

Abstract

This work presents the use of equiatomic high entropy alloy (HEA) particles as unconventional reinforcement phase in Mg matrix. Mg-HEA composites were fabricated by powder metallurgy method incorporating microwave sintering and hot extrusion. Recrystallized fine grains (∼50% reduction) were observed in all the composites due to the capability of HEA particles to serve as nucleation sites and for grain boundary pinning following extrusion. Grain refinement coupled with intrinsic high hardness of HEA particles led to an improvement in hardness of 47%, 51% and 54% in Mg-2.5 wt% HEA, Mg-5 wt.% HEA and Mg-7.5 wt% HEA composites, respectively. In comparison with traditional micron size reinforced composites, Mg-HEA composites displayed superior hardness improvement. In addition, HEA reinforcement particles also enhanced both tensile and compressive strengths of magnesium with marginally compromised tensile ductility and marginally enhanced compressive ductility. Relatively strong fiber texture of extruded pure Mg was weakened in the composites due to the presence of HEA particles effectively reducing the yield asymmetry to near unity in Mg-5 wt.% HEA and Mg-7.5 wt% HEA composites.