Role of plunge depth on the joint formation and mechanical behavior of Al6063‐AZ91 dissimilar lap joint produced by friction stir welding

Abstract

AbstractDissimilar lap joint of Al6063 aluminium and AZ91 magnesium alloys was successfully produced by friction stir welding. Three different plunge depths (3.2 mm, 3.25 mm, and 3.3 mm) were adopted during welding. Similar Al6063–Al6063 lap joints were also produced along with the dissimilar Al6063–AZ91 joints for the purpose of comparing the joint formation. With the increased plunge depth, the width of the similar Al6063 ‐ Al6063 lap joint was increased. On the contrary, joint width was decreased for the dissimilar joint with increased plunge depths. The dissimilar joint was formed with a strong metallurgical bonding between the Al6063 and AZ91 alloys, which is attributed to the mechanical mixing of these alloys in the nugget zone. Additionally, the formation of intermetallics was also observed from the x‐ray diffraction analysis. The variations within the measured hardness values were higher at the joint interface due to the mixing of aluminium and magnesium alloys in the nugget zone. From the tensile shear tests, increased strength and decreased elongation were measured with the increased plunge depth. The results demonstrate the importance of the plunge depth on the lap joint formation between dissimilar Al6063–AZ91 alloys during friction stir welding.