Effect of Refilling Time on the Microstructure and Mechanical Properties Refill Friction Stir Spot Welded 6082 Al Alloy Butt Joint

摘要

Abstract In this work, refill friction stir spot welding (RFSSW) is innovatively applied to butt weld 6082 Al alloys. The effect of the refilling time on the microstructure and properties of the welded joints was studied. The results show that for the 6082 Al alloy with a thickness of 2?mm, a tool plunge depth of 1.6?mm can successfully avoid the incomplete bonding at the joint bottom. Cracks, formed by insufficient bonding, appear at the tool retraction paths when using the short refilling times of 3?s and 4?s. A prolonged refilling time of 5?s can eliminate the crack due to sufficient diffusion time. The pin affected zone (PAZ) has coarser grains than the sleeve affected zone (SAZ) due to the insufficient tool stirring action. Prolonged refilling time results in coarser grains, lower hardness and higher tensile strength of the joints. The maximum tensile strength of 262.2?MPa is obtained when the refilling time of 5?s is used, and the joint fails at the heat affected zone (HAZ) under such a condition.