Laser repetitive pulse heating and phase change at the irradiated surface

Laser repetitive pulse heating of steel is modelled and the phase change process in the irradiated region is simulated. Temperature fields as well as the size of the melt and mushy zones are predicted in the irradiated region. The laser pulse duty cycle used in the simulations is selected to be comparable to that used in the industry. It is found that ripples occur in the temperature profiles as similar to the repetitive pulses. However, temperature difference in each ripple changes with time, provided that temperature difference becomes small during the phase change process. As the depth below the surface increases, the size of the ripples reduces due to the diffusional energy transport in this region. The size of the melt zone is larger than that of the mushy zone, which is particularly true along the symmetry axis.