Interface Behavior of Aluminum Alloy by Multipass MIG Welding

Al-Mg alloy plates with 8 mm thickness were welded by multipass MIG welding with the self-made wires as filler material, and microstructure of the welded joint were examined by metallographic, scanning electron microscope (SEM), X-ray diffraction and electron backscatter diffraction (EBSD). The results show that the weld zone is typical casting microstructure with no obvious preferred orientation. Comparatively, grains are more inclined to epitaxial growth, and the texture in reheating coarse grain heat-affected zone is more obvious than fine grain layer and weld zone because of the comprehensive additive effect of welding thermal cycle and the structural similarity on the interface during multipass welding. Besides, the grain growth is more apparent, microhardness is lower, and the residual stress value is only second to weld bottom, which is the weakest link.