Numerical simulation and experimental investigation of subzero liquid SFSW of ME20M magnesium alloy

Subzero liquid submerged friction stir welding (SFSW) on Magnesium alloy is an investigate limited in the past. As an important lightweight alloy with enhanced yield strength and heat resistance, ME20M Mg alloy has potential value to be researched. In this paper, numerical and experimental subzero SFSW were carried out to systematically investigate the thermal histories, the microstructures and the mechanical properties. The solution of dry ice and ethanol was employed to be the cooling liquid, and different cooling temperatures were employed on low-temperature SFSW of ME20M Mg alloy. The results show that the simulated temperature curves and the experimental temperature curves are closed and within 5% error; as the increasing of the heat input, the precipitations reduced and grew up, the tensile strength of the joints first increased and then decreased, the microhardness of the weld joint decreased. The largest tensile strength is 165.8 MPa, about 69.08% of the base metal. The highest hardness was the peak hardness of the smallest ω/v in WNZ, the lowest hardness located at HAZ of the AS of the largest ω/v, and the values were 57.1 HV0.1 and 44.1 HV0.1, respectively.