Verification of a new cellular automata model of solidification using a case study on the columnar to equiaxed transition previously simulated using front tracking

Developing computational tools appropriate for modelling physical phenomena, such as alloy solidification, requires making optimisation decisions on the time and spatial scales that can be resolved with finite compu-tational resources. Here we report on development of a model of grain nucleation and growth, based on a Cellular Automata (CA) approach, that can directly simulate columnar and equiaxed solidification, and their competition to trigger a columnar-equiaxed transition (CET), at the scale of a casting. Previous work has been to develop a Front Tracking (FT) model of columnar solidification and an equiaxed index capable of predicting the relative likelihood of CET formation in a casting case study. This FT model has been validated by extensive experimental studies. Here we apply the new CA model and compare the predictions to those of the FT model. The close agreement between the two models serves to verify the new CA model. The study also presents insights into the thermophysical phenomena affecting grain structure evolution in alloy solidification and confirms the validity and utility of the equiaxed index.