New method to improve the microstructure and mechanical properties of joint obtained using FSW

Abstract

Frictional heat combined with controlled forging pressure is applied during friction stir welding (FSW) to produce high-integrity, defect-free, and full penetration welded joints. Different methods have been applied to modify and enhance the different characteristics of weld obtained using FSW. In the current research, AA6061-T6 aluminum alloy workpieces were vibrated during FSW normal to welding direction while cooling intensity was also increased by application of water. Microstructure and mechanical properties of welds were investigated and compared with those friction stir welded conventionally. The results showed that the stir zone grain size decreased and weld strength, hardness, and ductility increased significantly as vibration and coolant were applied simultaneously. It was concluded that vibration increases the straining in stir zone and coolant decreases the stir zone temperature. The former has an effective role on grain refinement and the latter decreases the decomposition of Mg2Si precipitates. Both lead to the strength and hardness increase.