Dynamic evolution analysis on molten pool: LMD experiment and simulation

Laser melting deposition is an advanced additive manufacturing technology, wherein molten pool as the fundamental building block endures melting and solidification with complex heat and mass transfer, thereby significantly affecting microstructures of the formed parts. Through deposition experiments and numerical simulations, dynamic evolution of molten pool is investigated from initial molten status to final stable deposition, and microstructures generated there are illustrated by experimental morphological assessment and predicted based on numerical analysis of temperature gradient and solidification rate. Results show that molten pool presents the lengthy elliptical form, and temperature field appears elliptical with a trail at the rear portion, and temperature gradient perpendicular to the scanning direction is relatively higher. Marangoni vortices emerge at the onset of the flow field and subsequently transition into lateral flow and longitudinal vortex. Microstructures grow from planar grains and epitaxial columnar grains to equiaxed grains from bottom to top of molten pool.