Dual beam laser keyhole welding of steel/aluminum lapped joints

Laser welding of Q235 low carbon steel and 6061 aluminum (Al) alloy was carried out by using a dual beam fiber laser in keyhole welding mode in a steel-on-Al lapped configuration. The influence of processing parameters of power distribution ratios (Rs) and dual beam laser distances (d1) on the weld shapes, microstructures of intermetallic compound (IMC) layers, microhardness and tensile resistance of the steel/Al joints was studied. Soundly welded steel/Al joints have been achieved by using dual beam laser keyhole welding at Rs = 0.67 and d1 = 1.5 mm. The key factor affecting welding defects is the control of the penetration depth of the welds, and good weld shape has been achieved when the penetration depth of the welds is below 700 m. The formation of IMC phases consisted of Fe4Al13, Fe2Al5 and FeAl2 phases is only limited to the weld/Al interface when the steel/Al joint has a relatively low penetration depth of the welds in the steel/Al joint. The maximum tensile resistance of the steel/Al alloy joints of 115.6 N/mm is obtained under the conditions of Rs = 0.67 and d1 = 1.5 mm. The fracture surface reveals a mixed failure occurred in the Al alloy leading to high tensile resistance of the steel/Al joints.