Microstructure and mechanical properties of AZ31B Mg alloy fabricated by friction stir welding with pulse current

The influence of pulse current on microstructure and mechanical properties were investigated for friction stir welding (FSW) of 3 mm thick AZ31B Mg alloy with pulse current ranging from 0A to 400A. The grain size of SZ is the same of that of TMAZ as affected by pulse current, resulting in more smoothie transition of microstructure from the SZ to the HAZ. The ultimate tensile strength and elongation of EFSW joints both enhanced with increasing pulse current and fracture position shifted from SZ to HAZ. The EFSW joint has the highest hardness at pulse current of 300A, where a large quantity of precipitates consisting of Al and Zn elements that were refined without coarsening were uniformly distributed in grain boundaries, contributing to precipitation hardening effect, which is main strengthening mechanism for enhancing mechanical properties of the EFSW joints.

Automated summary

The influence of pulse current on microstructure and mechanical properties of FSW joints was investigated, with an increase in pulse current resulting in enhanced ultimate tensile strength and elongation of EFSW joints. The highest hardness was observed at a pulse current of 300A, with precipitation hardening being the main mechanism for strengthening the joints.