Grain refinement to submicron regime in multiaxial forged Mg-2Zn-2Gd alloy and relationship to mechanical properties

We elucidate here the impact of multiaxial forging of Mg-2Zn-2Gd alloy on grain refinement to sub-micron regime and relate the structure to mechanical properties. As-cast and annealed samples were multiaxial forged (MAF) for a total number of two passes with a true strain of ~2/pass. Using only two passes, multiaxial forging successfully reduced the average grain size to less than a ~1 µm. When the annealed samples were forged, the yield strength increased to ~227 MPa as compared to the as-cast alloy with yield strength of ~54 MPa. The improvement in mechanical properties is attributed to the homogeneous structure obtained on annealing, which led to high degree of grain fragmentation. Annealing also led to fine distribution of precipitates, which significantly improved strength and hardness. The Rockwell hardness (HRE) was ~88 for annealed and forged alloy in relation to ~55 for the as-cast alloy.