Effects of holmium and hot-rolling on microstructure and mechanical properties of Mg-Li based alloys

A rare earth holmium (Ho) element was introduced into Mg-8Li-3Al alloy to investigate the effects of holmium and hot-rolling on the microstructure and mechanical properties of the Mg-Li based alloys. Both alloys with and without Ho showed a duplex structure with alpha and beta phases. The as-cast Mg-8Li-3Al alloy exhibited a yield strength (YS) of 111.1 MPa, ultimate tensile strength (UTS) of 148.2 MPa and an elongation of 9.50% while the hot-rolled Mg-8Li-3Al-3Ho alloy had a yield strength of 249.7 MPa, ultimate tensile strength of 293.1 MPa with an elongation of 21.40%. These results indicated that both strength and ductility could be significantly enhanced by addition of holmium together with thermo-mechanical treatment. It was found that the microstructure could be refined significantly and the fracture modes changed from partial brittle to ductile fracture due to the addition of holmium. The effects of microstructure refinement, work hardening and solid solution strengthening induced by the addition of holmium and hot-rolling on the mechanical properties were discussed.