Laser-Material Interactions in Metal Additive Manufacturing*

Complex hydrodynamics driven by vapor recoil and Marangoni convection lead to non-uniform liquid metal interfaces which can form voids or roughness upon rapid solidification. To clarify the physics involved and establish pathways towards mitigation, in situ X-ray and optical imaging are used to study the dynamics of keyhole pore formation and surface morphology evolution in Ti and Al alloys. The experimental observations are compared to microscale hydrodynamic finite element modeling which captures the laser-melt pool interaction through ray tracing and predicts melt pool depths accurately.