Thermomechanical Simulation of Laser Powder Bed Fusion for Ti-6Al-4V: A Study on Residual Stress and Impact of Laser Process Parameters Using Volumetric Heat Source

Laser powder bed fusion (LPBF) is one of the most beneficial manufacturing methods for its precision and ability to create parts with complex geometry, although high thermal gradient due to the considerable temperature difference between ambient and peak temperature appeared during laser scanning causes high residual stress which can lead to serious damages during the process. Moreover, due to the unique application of Ti-6Al-4V, it is crucial to guarantee that the final product is precisely manufactured in its dimensions. Therefore, controlling the effective input parameters of LPBF is necessary to tackle or minimize the issue. An accurate simulation model can greatly enhance the ability to predict the residual stress and optimize the parameters aiming to achieve optimal mechanical properties while reducing costs and minimizing material usage. In this study, the role of an appropriate heat source on simulation results was investigated with the help of developing a simulation model based on the finite element method (FEM) using COMSOL Multiphysics software. Moreover, the effect of important process parameters, including laser power and velocity on deposited pool geometry and residual stress along the scanning direction was studied. Temperature-dependent properties and phase change were considered during the simulation to improve the outcomes. The results showed that increasing the laser power and decreasing laser scanning velocity can result in higher maximum temperature and wider deposited area in both depth and width. However, the effect on residual stress is complex and depends on various factors. According to the results, elevating the laser power tended to result in increased residual stress levels. But as the laser velocity increased, initially there was a decrease in residual stress. However, beyond a certain level, the trend reversed, and increasing velocity led to higher residual stress. The simulation model was validated by comparing it with the experimental results obtained from previous literatures.