Investigation of microstructure and residual stress development during laser surface melting of AH36 steel using 3-D fully coupled numerical model

Abstract

In this study, the microstructure and residual stress development during the laser surface melting process is investigated using a three-dimensional fully coupled numerical model. With a fully coupled model, unlike a sequentially coupled model, the evolution of the temperature, melt flow, microstructure, and stress fields during the entire melting process is computed by directly accounting for their mutual interactions. Therefore, the developed numerical model can reflect the actual laser melting process and predict the solid-state phase transformation and stress development during the process. Laser surface melting experiments are performed on AH36 steel using a 2 kW fiber laser with a rectangular top-hat profile. Residual stresses are measured using the contour method, and the microstructure distributions are examined using an optical microscope. Three process conditions are examined, including a high laser energy condition and an extremely low processing speed, to validate the model. The simulation results agree well with the measurement data.