Quantitative 3D mesoscopic modeling of grain interactions during equiaxed dendritic solidification in a thin sample

A 3D mesoscopic envelope model is used to numerically simulate the experimental X-ray observations of isothermal equiaxed dendritic solidification of a thin sample of Al-20 wt % Cu alloy. We show the evo- lution of the system composed of multiple grains growing under influence of strong solutal interactions. We emphasize the three-dimensional effects in the thin sample thickness on the growth kinetics, focusing on three aspects: (i) the impact of the third dimension on the solute diffusion, (ii) the influence of the orientation of the preferential grain growth directions <100> on the interactions with the confining sample walls, and (iii) the influence of the grain position along the sample thickness. We demonstrate the importance of considering the three-dimensional structure of the thin samples despite the small thickness. We further show that the mesoscopic envelope model can accurately describe the shape and the time-evolution of the equiaxed grains growing under influence of strong solutal interactions.