Effect of laser beam models on laser welding–brazing Al to steel

Abstract

Joining dissimilar metals Al to steel in butt configuration was successfully realized by laser welding–brazing process with different laser beam models (single laser beam, cross and in–line dual laser beams). Undercut occurred at the joint produced by single laser beam and satisfactory weld formations were obtained in the joints produced by cross and in–line dual laser beams. Dual laser beam was beneficial for the reduction of interfacial intermetallic compound (IMC) thickness and homogenization of interfacial IMC morphology. Numerical models were developed to calculate the thermal cycles along brazing interface. Calculation of interfacial thermal cycles revealed that lowest peak temperatures (1028 °C, 1036 °C and 990 °C respectively for top, middle and bottom regions), shortest time of interaction at high temperature (2.2 S) and smallest temperature gradients (1036–990 °C = 46 °C) were all obtained in the joint produced by cross dual laser beam and these all made contribution to its thinnest and most homogeneous interfacial IMC. Joint with the highest tensile strength was produced when the cross dual laser beam was adopted due to its satisfactory weld formation and most homogeneous of τ5.