Improving the tensile properties of extruded Mg–Ga alloy by ageing treatment

A hot-extruded Mg-5Ga alloy was subjected to ageing treatment at 150 ​°C, 190 ​°C and 230 ​°C. The microstructures and mechanical properties of the extruded and aged alloy were examined in this study. Microstructure examinations suggested that particle-shaped and rod-shaped Mg5Ga2 were precipitated in the alloy after peak ageing treatment. The extruded alloy showed the yield strength, ultimate tensile strength and elongation to fracture of 157.6 ​MPa, 248.6 ​MPa and 17.5%, respectively. After peak ageing, the yield strength and ultimate tensile strength can be enhanced by as much as 15.7% and 8.6% reaching 182.3 ​MPa and 270 ​MPa, respectively. The improvement of the tensile strengths is mainly attributed to the enhanced precipitation strengthening by newly formed fine Mg5Ga2 precipitates. The ductility of the alloy was slightly increased by peak ageing at low temperatures (150 ​°C and 190 ​°C), but remarkably decreased by peak ageing at high temperature (230 ​°C) due to the formation of coarsened Mg5Ga2 particles which easily initiated the cracks during tensile deformation.