Finite volume modeling and experimental analysis of keyhole dynamics, temperature field and weld characterizations of Ti-6Al-4V tubes with unequal thickness in fiber laser welding

This study examined the laser welding of Ti-6Al-4V titanium alloy tubes using a combination of experimental and numerical methodology, with the objective of elucidating the effects of process parameters on temperature distribution, keyhole dynamics, and material phase transitions. A computational fluid dynamics (CFD) model was created to simulate heat transfer, melt flow, and keyhole dynamics employing the finite volume method (FVM) and Volume of Fluid (VOF) approaches. Experimental examination was performed via fiber laser welding on titanium tubes of differing thicknesses, with temperature measurements obtained through thermocouples and sophisticated imaging techniques. The temperature field from the fusion zone to the base metal, keyhole dynamics, and weld bead characterization were assessed in the keyhole laser welding process in thickness from 1 to 2 mm, welding speeds from 0.094 to 0.146 m/min, and beam deflections ranging from −0.2 to 0.2 mm and laser power from 300 to 800 W. The numerical solution outcomes demonstrated that a reduction in speed, an increase in power density, and an augmentation of the thickness ratio significantly elevated the temperature distribution. A decline in speed of 2 degrees per second resulted in a raising of the maximum temperature to 220 °C. The microstructural variation according to the high heating and cooling rate induced by laser welding created a different microstructure including acicular α′ martensite, incomplete transformation to α′ phase for HAZ region in different parts from molten pool toward base metal.