Heat transfer modelling of rapid solidification on a substrate. A parametric investigation for large undercooling

A parametric investigation of the heat transfer and phase change during splat cooling has been conducted with a non-equilibrium model. This model is able to track the solid/liquid interface motion for rapid solidification with large undercooling. Some results are shown to illustrate the level of uncertainty introduced by the use of linearized kinetics models. The influence of various parameters (such as nucleation temperature, splat/substrate thermal contact, melt and substrate materials, kinetics coefficients, initial substrate temperature, and initial melt temperature) on the solidification interface temperature and velocity has also been investigated. The related physical mechanisms are discussed in terms of heat transfers and temperature distributions. One important effect quantified in this study is the fact that both the interface velocity during recalescence and the fraction of the splat affected by recalescence depend not only on the nucleation temperature but also (and very strongly) on the undercooling distribution across the splat upon nucleation. For instance, a relatively high nucleation temperature and small temperature gradients in the splat may well result in a higher solidification rate away from the substrate than a very low nucleation temperature and large temperature gradients in the splat. Interestingly (and somewhat counterintuitively) one might then achieve in some cases higher solidification rates in the splat for poor thermal contact between the splat and the substrate than for good thermal contact, all other parameters (including nucleation temperature) being equal.