Microscale investigation of molten pool flow and microstructure evolution of Inconel718 alloy during solid-liquid transition

Abstract

In Laser Direct Energy Deposition (L-DED), the heat and mass transfer within the molten pool significantly impact the evolution of dendritic structures and the surface characteristics of the deposited components. To advance the study of the solid-liquid transition, a numerical model that simulates molten pool flow and solidification is essential. Parameters derived from solidification are integrated with the phase field model to simulate dendrite growth during the solid-liquid transition. Furthermore, to validate the coherence between numerical simulations and experimental observations, numerous single-track samples were produced using L-DED. It is anticipated that the flow direction of the molten pool will be influenced by heat convection and powder disturbances. As the laser moves and heats the material, the volume of the melt pool increases gradually, and the pool's shape remains symmetric along the direction of motion. The temperature gradient has a significant impact on the dendrite tip growth rate. During nucleation, dendrites develop in an ultra-cold solution. Dendritic competition and growth interact, leading to variations in dendritic size and growth rates. Due to insufficient solute diffusion within the dendrite, the solute concentration in the dendrite remains elevated.