Thermo-Mechanical Simulation of Ti6Al4V-NiTi Dissimilar Laser Welding Process

Fiber Laser Welding (FLW) is a versatile joining technique of metals and alloys because it allows welding of dissimilar materials without filler material. FLW utilizes intensified heat energy to liquify the workpiece interface and joins when they are solidified. In this study, dissimilar joining between Ti6Al4V-Nitinol was performed using FLW process and the thermomechanical model was developed to understand the metallurgical mechanisms and investigate weldability of dissimilar alloys. The FLW of Ti6Al4V and Nitinol plates was performed with variable power density, welding speed, and focal distance. In this three-dimensional numerical model, heat flows in two different workpieces were computed during active laser welding and cooling process using a combined effect of radiation and convection. Both of the top and bottom surfaces of the welded zone were studied considering the combined effect from focused heat source and Argon shielding gas. Significant thermal cracks were produced through the welded interface. However, this numerical study illustrated thermomechanical foundation and discuss future challenges to improve the integrity and desirable FLW parameters in the dissimilar metal joining.