Microstructure and stress distribution of narrow-gap rotating laser welding thick Al-Mg alloy joint

摘要

The microstructure and residual stress distribution of the 15 mm-thick 5A06 aluminum joint welded by narrow-gap rotating laser welding were investigated. The results show that the rotating laser can obviously decrease the porosity of the 5A06 aluminum joint. The weld metal (WM) mainly consists of the solidification structure, while the base metal (BM) and the heat affected zone (HAZ) present a rolling banded structure. The second phase in WM is dispersively distributed Mg5Al8, but BM and HAZ also contain (FeMn)Al-6 and Mg2Si. Although the lowest ultimate shear strength tau(u) was found in WM, its shear plasticity a is better than that of BM and HAZ. The maximum temperature of HAZ is higher than 280 degrees C, which exceeds the recrystallization temperature of 5A06 aluminum. Furthermore, the distribution of residual stress along the thickness direction shows a bimodal appearance.