Investigating governing parameters influencing solidification process in pulsed laser micro-welding of AISI 316L thin foils using finite element method

This research aimed to study the governing parameters influencing the solidification of AISI 316L thin foils during pulsed laser micro-welding in the lap-joint configuration. Therefore, a three-dimensional finite element model was developed to investigate the effects of power, pulse duration, and frequency of the laser beam on the governing parameters of the microstructure at a constant speed. Moreover, to consider the final microstructure as well as verify the numerical results, a set of experiments was designed and carried out based on the response surface method. The results show that the pulse time has the most significant effect on the temperature gradient and solidification rate, and consequently on the cooling rate and morphological parameter. Furthermore, the pulse time and peak power have a significant interaction effect on the temperature gradient. Although the pulse time and the peak power have a significant effect on the solidification rate at the weld centerline as well as the fusion line, they show a considerable interaction effect just in the weld centerline. The cooling rate and morphological parameters, two governing solidification parameters, are mostly and minimally influenced by the pulse time and frequency. Increasing the pulse time, power, and frequency decreases the cooling rate, resulting in a coarser microstructure. At the same time, increasing the processing parameters decreases the morphological parameter in the weld centerline; however, a slight increase occurs at the fusion line. A comparison of the numerical and experimental results showed a good agreement.