Microstructure and Mechanical Properties of 6061 Aluminum Alloy Welded by Fiber Laser Beam Welding

Abstract

6061 aluminum alloy was welded by fiber laser beam welding. The microstructure and mechanical properties of welded joints were analyzed. The results show that the microstructure distribution of welded joints is inhomogeneous and the mechanical properties in different zones of joints are non-uniform. Fine columnar microstructure is formed near the fusion line and the fine equiaxed grains distribute in the center of the weld. The weld is consisted of α-Al matrix phase and (α-Al + Si) eutectic structure. Microhardness of the weld metal is lower than that of the base metal. Tensile test indicate that the fracture of all welded joint occurs near the fusion line, and the ultimate tensile strength of the joints may reach about 80% of the base metal. Fractography of the weld joints is found to be dimple, which means that the fracture feature is ductile. Suitable heat treatment after welding can improve the combined mechanical properties of the joints.