Investigation of Homogeneity of Chemical and Mechanical Properties in Laser-welded Dissimilar Steel-aluminum Joints

Dissimilar joining between steels and aluminum alloys becomes increasingly important to assemble light weight automotive structures. In this study, laser welding was conducted to join an AISI 1005 low carbon steel to an AA1100 wrought aluminum. 2 typical homogeneous and inhomogeneous fusion zones at the laser-welded joint between steel and aluminum were intensively investigated by microscopic observation and nanoindentation test. Homogeneous fusion zone showed gradual variations of chemical compositions and hardness distribution in the weld bead, which improves tensile shear strength. On another hand, inhomogeneous fusion zone showed 2 distinguished fusion zone, with different chemical compositions, hardness and reduced Young's modulus distributions, which could promote cracks at the interface in the fusion zone and deteriorate joint strength.