Effect of temperature-dependent physical properties on finite element modeling of laser welding of titanium alloy

This study investigates the effect of using temperature-dependent and constant thermophysical properties on the precision of numerical simulation in the laser welding of titanium Ti60 alloy. A finite element model is made for 3 mm thick Ti60 alloy sheet piece and is affected by the laser beam using a three-dimensional moving heat source. For verification of the finite element model, the numerical results are compared with the results of experimental data. Also, the influence of the number of elements on the results is investigated. The results of the finite element modelling showed that the solidification starts from the bottom of the melt pool and progresses to the top of the sheet and along the weld seam. Also, the best results are obtained with all the thermophysical properties of density, thermal capacity and conductivity were temperature-dependent. The use of constant density reduces the maximum values of the temperature and dimensions of the weld pool, and the use of constant heat capacity increases these values. Still, these changes are such that (less than 2%), constant density and thermal capacity can be used to model the whole laser welding process. However, the use of constant thermal conductivity causes a large error in the maximum values of the temperature (about twice the value of this parameter), and the dimensions of the melt pool, and this parameter cannot be assumed constant in the simulation of laser welding.