On the role of confinement on solidification in pure materials and binary alloys

We use a phase-field model to study the effect of confinement on dendritic growth, in a pure material solidifying in an undercooled melt, and in the directional solidi. cation of a dilute binary alloy. Specifically, we observe the effect of varying the vertical domain extent (delta) on tip selection, by quantifying the dendrite tip velocity and curvature as a function of delta, and other process parameters. As delta decreases, we find that the operating state of the dendrite tips becomes significantly affected by the presence of finite boundaries. For particular boundary conditions, we observe a switching of the growth state from 3D to 2D at very small delta, in both the pure material and alloy. We demonstrate that results from the alloy model compare favorably with those from an experimental study investigating this effect.