Extraordinary Strengthening of Magnesium by Solid-State Diffusion of Copper in Mg-0.5Cu Alloy

A powder-processed hot-extruded high-performance Mg-0.5 wt.% Cu alloy has been developed by solid-state diffusion of elemental copper into commercially pure magnesium powder. Copper, in nanoparticle form, was blended to form a dry-coat layer on micrometer-size magnesium particles, which subsequently homogeneously diffused, forming a single-phase solid solution during the sintering process. Copper as a solute atom did not act as a grain refiner. Investigation of the mechanical properties revealed that the strength properties of commercially pure magnesium were significantly improved (macrohardness by 32.5%, microhardness by 42.7%, tensile yield strength by 114%, tensile strength by 69%, compressive yield strength by 46%, and compressive strength by 48%) due to the dissolution of copper as solute atoms. The ductility of the magnesium suffered marginal loss despite the fracture mode being ductile, which was due to decohesion at the magnesium interparticle boundaries induced by the relatively higher copper concentration.