A front-tracking solidification model and its application in modelling alloy solidification

Abstract

A front-tracking solidification model has been developed to simulate the dendritic structure evolution during alloy solidification. In the model the growth of dendrites is governed by heat and mass transport and a finite difference technique is employed to solve heat and solute diffusion during solidification. The model incorporates front-tracking technique to calculate and track the exact position of the Solid/Liquid (S/L) interface as a part of solution process and a new capture rule was designed and implemented in the model to efficiently track the growing S/L interface. The model has been evaluated and verified using simulated data from Al-Cu 4 wt. % alloy solidification. The effect of curvature undercooling on crystal growth was investigated. The simulated results reveal that solute redistribution, curvature of the S/L interface and anisotropy of interface tension are important factors in determining the dendritic morphology. The calculation of the S/L interface curvature and anisotropy of surface tension was found to be particularly important in determining the dendritic growth direction. Based on the above observations and simulated data, the parameters in the developed model have been optimised for predicting the solidification structure in binary alloys. Simulations of Al-Cu alloy solidification were then performed using the optimised model for single-grain and multi-grain solidification. The simulated results of single-grain growth were compared with the results from the Lipton-Glicksman-Kurz (LGK) model (Lipton et al. 1984). Solute profile ahead of the S/L interface was examined using different techniques for approximating solute profile in the growing cell. The solidification segregation in the multi-grain growth was investigated; and the dendritic evolution and solute interaction during multi-grain growth were investigated