On the Immersed Friction Stir Welding of AA6061-T6: A Metallurgic and Mechanical Comparison to Friction Stir Welding

Abstract

The objective of this research was to quantify the material properties as well as the forces unique to immersed friction stir welding (IFSW) as compared to conventional friction stir welding (FSW) performed in air on AA6061. Two experiments were preformed at the Vanderbilt University Welding Automation Laboratory using different tools weld coupons for conventional friction stir welds and immersed friction stir welds. The results of the submerged welds were compared to conventional welds and include comparison of planar and axial forces, moments or torques, welding temperatures via thermocouple implantation, and the ultimate tensile strength (UTS) at optimal welding conditions. The experimental results compared were for AA6061-T6 welded at rotational and travel speeds of 1000-3000 rpm and 5-16 ipm in the full penetration butt weld configuration. Results conclude that immersed friction stir welds increase ultimate tensile strength by approximately 5% (15 MPa) and micro-hardness by 10% (8 HV) while maintaining other comparable properties. A verified steady state 3-dimensional thermal model of the friction stir welding tool was developed for the purpose of discovering the contribution of quench rates on the temperature distribution.