Forgeability, microstructure and mechanical properties of a free-forged Mg-8Gd-3Y-0.4Zr alloy

A Mg-8Gd-3Y-0.4Zr (GWK830, G, W, and K refer to Gd, Y and Zr respectively) alloy was free-forged, and the effects of forging temperature and total deformation on forgeability, microstructure and mechanical properties of the alloy were investigated. For forgeability, the suitable temperature is above 380 °C, and a total deformation up to 45% is acceptable at 430 °C. With forging temperature increasing from 380 °C to 430 °C, considerable dynamic recrystalization (DRX) took place at the expense of twinning, resulting in the improvement of mechanical properties. But at 480 °C, complete DRX grains fully consumed the deformation twin and coarsened, leading to the decrease of tensile properties. Holding the forging temperature at 430 °C and raising total deformation, DRX and texture with c-axis of most grains normal to elongation direction (ED) were intensified evidently, accounting for the increasing mechanical properties along ED and the texture also enhanced the anisotropy of tensile properties between ED and forging direction (FD). Furthermore, yield strength (YS) of 276 MPa, ultimate tensile strength (UTS) of 353 MPa and elongation of 9.25% were obtained when the free-forging was carried out under a temperature of 430 °C and a total deformation of 45%.