Forming Property and Microstructure in Dissimilar Thickness Friction Stir Weld of Al Alloy 5052

This study examined effect of microstructure on the forming property in dissimilar thickness friction stir welds of 1mm- and 2mm-thick Al alloy 5052 sheets with three different cross-sectional features, i.e., weld without lazy S, weld with lazy S and weld with kissing-bond. The weld with kissing-bond cracked during root bending. The other welds containing the lazy S did not fail during bend testing. Microstructural analyses suggest that local distribution of oxide particles does not cause the cracking at the initial butt surface during root bending.