Analysis of Fiber-Laser Welding of Ti6Al4V via Experiments and Predictive Modeling

A single mode continuous wave ytterbium fiber laser welding process was investigated for Ti6Al4V alloy sheet joining using lap configurations.    The effect of welding speed and laser power on surface morphology, welding defects, microstructure, hardness and weld strength is presented. In the study, the power level and welding speed is chosen to produce consistent weld geometry in terms of penetration depth and weld width.   The investigation compares experimental results of microstructure change, weld strength through peel testing and weld defects between low power and high power welding.  The computational model is used to explain the fluid flow characteristics in the weld pool, keyhole formation and pore formation. In addition, the temperature field evolution in the computational model is used to show the phase transformation in the fusion zone and heat affected zone. The model predicts the microhardness in the work piece by computing the phase transformation in the fusion zone and heat affected zone. The model is used to test whether same findings can be scalable to high power >10kW laser ytterbium fiber laser welding. Different characteristics in the microhardness, keyhole formation, and fluid flow in high power regimes is explained through modeling results.