Quantitative Study on the Dynamics of Melt Pool and Keyhole and Their Controlling Factors in Metal Laser Melting

Recent direct visualization of keyhole morphology evolution by ultrahigh-speed synchrotron X-ray imaging provides fascinating insights and basis for further understanding and investigation of the melt pool (MP) behavior during laser melting. By combining the ray-tracing method, the phase field method and the lattice Boltzmann method, we simulate the laser melting process of Ti-6Al-4V plates quantitatively and predict five distinct regimes observed experimentally, and uncover the underlying dynamics and controlling factors for each regime. Remarkably, we also reveal four types of distinct oscillations of the MP and their underlying mechanisms. The 3D irregular oscillation of keyhole tip is identified to be responsible for bubble spill-over. These revealed dynamics and their underlying controlling factors provide a solid physical foundation for controlling laser-based 3D printing processes.