Experimental researches on resistance heat aided friction stir welding of Mg alloy

Abstract

Resistance heat aided friction stir welding (RFSW) was utilized in this experiment with the combined effects of friction heating and resistance heating by adding the direct electric current (0-160 A) to the AZ31B magnesium alloy butt joint. The welded joints were described by optical microscope observations. Analysis of the grain boundary character distribution by optical microscope showed that the weld zone defects decreased, and smoother and more compact joint appearance was accessed by combining the direct electric current with the conventional FSW. In addition, raising the value of electric current promoted the joint quality and refined the grain size in the weld nugget zone (WNZ) and thermo mechanically affected zone (TMAZ) dramatically. However, since there are more grain growth and secondary recrystallization in HAZ of RFSW joints, the average grain size is larger than that of conventional FSW joints. The travel speed of 30 mm/min and the current value of 160A were optimum options within the parameters investigated in this work.