A model for nanoparticle transport and distribution with particle-interface interaction during binary alloy solidification

Abstract

The interaction between nanoparticles and the solid-liquid interface during the solidification of binary alloys containing nanoparticles affects the nanoparticle transport and subsequently the final nanoparticle distribution and solid growth. Thus, a model to capture the engulfment or pushing of nanoparticles by the interface and the resulting change in nanoparticle transport and distribution is important. In this work, a numerical model to capture the nanoparticle transport and solute transport during the micro-scale solidification of binary alloy containing nanoparticles is presented. To develop the model, a sharp interface enthalpy method-based solidification model is used. The nanoparticle transport is governed by nanoparticle diffusion due to Brownian motion and by nanoparticle engulfment/pushing at the interface. The nanoparticle engulfment or pushing is modeled as a function of critical engulfment velocity and interface velocity. Thus, the effect of nanoparticle size and local interface movement velocity on nanoparticle engulfment can be predicted by the model. Simulation results show poor engulfment of smaller nanoparticles and relatively higher engulfment of larger nanoparticles. This results in slower dendrite growth rate in presence of smaller nanoparticles. It is also observed that as the dendrites grow, there is a transition from engulfment of nanoparticles to pushing of nanoparticles. This transition depends on the nanoparticle size and is delayed for larger nanoparticles. Thus, more uniform distribution of larger nanoparticles is observed in the solidified binary alloy nanocomposites.