Friction stir welding of AA-5754 in water and air: A comparative study

Abstract

The present research work is conducted to examine the effect of rotational speed on the microstructure and mechanical properties of aluminum alloy-5754 (AA-5754) - H 22 during friction stir welding (FSW) in water and air. The results of the study revealed defect free joints at different rotational speeds during FSW in water (UFSW) whereas FSW conducted in air resulted in defective joining at the rotational speed of 1120 rpm. Dynamic recrystallization in stir zone (SZ) composed of much finer and equiaxed grains were observed in both FSW and UFSW samples regardless of cooling medium and rotation speed. UFSW joints fabricated at different tool rotational speed revealed fine grains, better tensile properties and microhardness as compared to FSW joints. This improvement in mechanical properties during UFSW can be accounted for micro-structural changes and solid solution strengthening caused by low peak thermal boundaries.