Temperature field simulation and grain morphology on laser welding-brazing between Ti-6Al-4V and 1050 aluminum alloy

Laser welding-brazing (LWB) technique is considered to offer advantages over fusion welding in terms of dissimilar jointing since it can avoid liquid dissimilar alloys mixing in the molten pool. In this paper, LWB technique is utilized to join 1050 aluminum alloy to Ti-6Al-4V. A 3D finite element model is developed to calculate the temperature field in the LWB process with a combined Gaussian heat source model. The simulated asymmetric temperature field is in good agreement with the experimental metallography, which confirms the validity of the present combined heat source model. The peak temperature of the center of the weld seam increases with time in the welding process. The experimental and simulation results both indicate that the heat-affected zone (HAZ) width of the upper is narrower than that of the bottom. Besides, the growth orientation of coarsened dendrite near the interface at root face is substantially perpendicular to interface. The grain morphology of the molten pool appears as dendrite, cellular dendrite and equiaxed crystal from the fusion line to the center of the weld seam.