Influence of preheating temperature on the friction stir welded ME20M magnesium alloy

Friction stir welding (FSW) of ME20M magnesium alloy without and with preheating in different temperatures is carried out. The thermal histories of different preheating temperatures are investigated; the microstructure and mechanical properties of the weld joints are studied. The results show that by increasing the preheating temperature, the peak temperature, the grain size as well as the precipitate size are increased, and the precipitation is reduced. After FSW, the preferred orientation of the ⟨0001⟩ crystal direction changes not to parallel but to normal direction, and the texture intensity improves. The microhardness and the tensile strength of the joints first increase and then decrease with the increase of the preheating temperature.