# Prediction of Transient Temperature Distributions for Laser Welding of Dissimilar Metals
## 1 Introduction
Results reported that regardless of the disparity throughout thermal conductance of the components, the maximum temperature attained on the 304L portion of the varied weld-assemblage junction was higher than the maximal temperature obtained on the St37 carbon-steel portion. The maximal temperature variation of both materials lowers as backward from a welding-line [25]. Despite the fact that the source for heat energy is applied unevenly/uniformly throughout the numeric paradigm design, the temperature region curvature acquired for distinct laser-butt welding (DLBW) of 304L and St37 appears nonlinear and inherently unstable [25]. It was also discovered that the temperature profile both for identical and DLBW joints decreased dramatically close the weldment/welding-direction and then reduced marginally throughout the area farther aside toward a welding-line [25]. [PERSON] et al. [26] used the FORTRAN programming language for predicting weld geometry, temperature contour, and strain distribution of copper and steel of 2 mm thickness joined by disk laser. They concluded that among all temperature-dependent properties, specific heat and thermal conductivity have a higher impact in numerical simulation. [PERSON] et al. [27] studied temperature field and molten pool dimensions with respect to the thickness of Ti6 Al4V. The analysis indicated that the thin sheet decides an array for variables chosen throughout an attempt to attain an acceptable penetrating depth and breadth of melt pool [27]. Results indicated that the temperature and dimensions of such molten weld pool are significantly affected through altering a pulsed laser process variable. Reasonable weld bead quality was produced by selecting suitable process parameters. Because of the various cooling rates, the plate thickness now had the greatest effect on welding deviation. A comparatively low rate of cooling, caused by the thinner sheet producing a significantly greater temperature difference on the thin sheet, increasing pulsed laser power-beam source absorption as well as deviating a pool of molten metal against the thin sheet [27]. When the laser power density was reduced, the melting flow rate and temperature of the molten weld pool increased significantly more than when the other parameters were changed. The numerical simulations of temperature gradients matched the scientific evidential studies as well. Raising the weld speed to between 120 to 372 mm/min resulted in a significant reduction in the temperature of an adjoining proximity region of a molten weld zone between 280 and 98 \({}^{\circ}\)C for it and 0.1 cm thickness [27]. With 0.15 cm thickness, the temperature dropped from 224 to 68 \({}^{\circ}\)C. While the depth of a molten weld zone was the same across all thicknesses (0.1 and 0.15 cm), the breadth of a weld zone for 0.1 cm thickness was almost twice as large as the width of the melt pool for 0.15 cm thickness due to the orientation and slope of a weld zone toward the thinner layer [27]. Other research [28; 29; 30; 31; 32] assessed the transient temperature profile [20; 33; 34] of the weld materials utilizing finite element-based 3D models, considering various heat source models [35; 36; 37; 38]. There are very few works with COMSOL on this and the combination is not considered much in the previous literature. In the present work, the thermo-physical properties of both materials (AISI 316L and Ti6 Al4V) are considered to be temperature dependent and the interpolation method issued to obtain the properties in intermediate temperatures. Thereby, the transient (time dependent) 3D model in COMSOL is used to generate the geometry, mesh, isothermal contour, and temperature distribution along the weld line. Weld thickness is predicted for a fiber laser welding of dissimilar butt joints. For both AISI 316L and Ti6 Al4V, temperature dependent material parameters such as heat capacity, thermal conductivity, and density are taken into account. Transient isothermal contours help to understand the heating and cooling phenomena during the process.