Research on microstructure and corrosion properties of 6061 aluminum alloy laser welding

Abstract This paper analyzed the microstructure and properties of 6061 aluminum alloy laser weld seam, which focused on the effect of laser defocusing amount(LDA) on weld morphology, microstructure, and corrosion resistance. The microstructure and corrosion behavior were studied by scanning electron microscope (SEM), and electrochemical testing system. It indicated that corrosion behavior respectively correlated with the precipitated phase and LDA. Experiments confirmed that with the LDA set to +0.4 mm, the laser focal spot expands, and the weld seam microstructure exhibit better corrosion resistance,reaching the corrosion resistance of 63.23% of the BM. The precipitation of Mg 2 Si phases and the corrosion pits reduced to minimum levels by micro-galvanic corrosion. The weld width and the number of surface defects could be optimized by LDA adjustment. And the large LDA value coarsening the grain structure, dendrite spacing, and Mg 2 Si precipitates.