Effect of traverse speed in submerged friction stir welding ME20M magnesium alloy: microstructure and mechanical properties

As an important lightweight with enhanced yield strength and heat resistance, ME20M has potential value to be researched. Friction stir welding (FSW) on ME20M magnesium alloy were investigated limited in the past, and submerged friction stir welding (SFSW) of ME20M has been also limited studied. In this paper, different traverse speeds of SFSW of ME20M Mg alloy were carried out, and the microstructure and mechanical properties were studied. The results indicated that tunnel defects can be found when the friction heat was insufficient, and flashes reduced when the traverse speed increased. The dynamic induced precipitation occurred during the dynamic recrystallization. With the increase of the traverse speed, the quantities of precipitations decreased. The highest micro-hardness located at the weld nugget zone of the joint in the traverse speed of 50 mm min(-1) and the rotation speed of 1300 r min(-1), which is about 54.8 HV0.1. The lowest hardness 42.5 HV0.1 occurs at the advancing side HAZ of the weld joint when the traverse speed was 30 mm min(-1). The tensile strength of the welded joint is 167.8 MPa at the parameter of traverse speed 40 mm min(-1), about 69.9% of the base metal.