A model for predicting the effects of buoyancy driven convection on solidification of binary alloy with nanoparticles

Abstract

Convection during the solidification of a binary alloy with nanoparticles governs the nanoparticle, species and temperature distribution in the domain and thus the solidification rate and morphology. Hence, a numerical model to predict the effect of convection on solidification with nanoparticles is essential. In this work, a volume averaged enthalpy method-based model is developed to predict the nanoparticle, solute and temperature distribution during micro-scale solidification of binary alloy with nanoparticles. In addition to nanoparticle transport due to Brownian motion based diffusion, the effects of thermal buoyancy, solutal buoyancy and nanoparticle driven convection are considered in the model. The effect of nanoparticles on the solidification process is also incorporated into the model. From single dendrite simulations, it is observed that convection plays a significant role in dendrite growth and nanoparticle distribution. Also, it is observed that the effect of nanoparticle driven convection is insignificant. Microstructure simulations with large number of dendrites show that the effect of convection on the dendrite growth is diminished due to the reduction in space available for flow in the interdendritic region. It is also found that the presence of convection increases the homogeneity of nanoparticle distribution in the final microstructure.