Mechanical property and microstructural evaluation of friction stir welded AA8090 T87 aluminium alloy

Abstract

The aerospace alloy AA8090 T87 was friction stir welded with varying traverse speeds of 30 and 70 mm/min at rotation speeds of 900 and 1100 r/min to realize the effect of traverse speed and rotation speed on the joint strength. This variation in the rotation and traverse speeds produced variation in the thermal cycle in the weld joint that altered the microstructure of the stir zone and morphology of the grains. The increase in the rotational speed from 900 to 1100 r/min at 30 mm/min increased the grain size from 4.1 µm to 7.8 µm in the stir zone which was evident from the microscopy images and Schmid factor maps and contributed to the mechanical property changes. The increase in traverse speed from 30 to 70 mm/min has led to the hardness improvement and reduction in grain size in the stir zone. The nature of the fracture observed in the stir zone is ductile fracture having more dimples. An effective joint was produced at 900 r/min rotational speed and 30 mm/min traverse speed.