Effects of oscillating laser offset on microstructure and properties of dissimilar Al/steel butt-joint

Abstract

The key challenge in laser butt-welding of dissimilar Al/steel metals, i.e., unevenly-distributed brittle intermetallic compounds (IMCs) along the interface, was solved via the beam oscillation under optimized laser offset (∆D). The IMCs thickness variance from top to bottom (δ) was adopted to quantitatively evaluate the uniformity of IMCs layer. The smaller the δ, the better the uniformity. The δ decreased from 105.14 to 0.0022 as the ∆D increased from 0.4 to 0.8 mm, indicating the uniformity increased by 4.7 × 104 times. The uniformity enhancement nearly doubled the ultimate tensile strength of the joint, which increased from 77 to 160 MPa. The formation of the IMCs layer and the fracture failure process of the joint were discussed in terms of the melt flow in the molten pool and its effects on the element distribution at the interface.