Effect of Ca addition on the microstructure and the mechanical properties of asymmetric double-sided friction stir welded AZ61 magnesium alloy

The effects of 2% Ca addition on the microstructure and the mechanical properties of the asymmetric double-sided friction stir welded magnesium alloy AZ61 were investigated. Compared to the Ca-free AZ61 magnesium alloy, the addition of 2% Ca significantly refines the grains in the stir zone after welding. Due to the existence of thermally stable Al2 Ca particles, there is no noticeable change in the grain size in the stir zone regardless of the welding heat input. The electron backscattered diffraction analysis at the center of the stir zone confirmed the significant deterioration of the(0001) texture strength from the addition of 2% Ca. The tensile test of the joint suggested that the addition of 2% Ca provides stable tensile properties to the joint regardless of the welding parameters. The critical(0001) texture strength that determines the ultimate tensile strength decreased from 20 to 15 by the Ca addition. The addition of Ca enhanced the deterioration of the plastic elongation when the(0001) texture strength increased.