Numerical investigation of solidification and CET of the transparent alloy NPG-37.5 wt.% DC in microgravity “TRACE” experiment

A solidification experiment "TRACE" of the transparent alloy Neopentylglycol (NPG)-37.5wt.% D-Camphor (DC) was conducted on-board the sounding rocket TEXUS-47 in low-gravity environment to investigate the columnar growth and the columnar-to-equiaxed transition (CET). To improve the fundamental understanding of solidification and CET in microgravity, the current laboratory scale experiment was tried to be numerically reproduced by a recently developed 5-phase volume averaging model. The temperature gradient in the solidification cell is applied to the simulation. In absence of melt flow, the calculated cooling curves, columnar tip position, tip undercooling and velocity, and number density of equiaxed crystals were compared to the results of in-situ real-time observations of the experiment. The CET could be predicted at position close to that of experiment. Simulation reveals the competitive growth between the columnar and equiaxed crystals before CET. Modelling parameters of equiaxed nucleation and columnar tip growth are the key to regulate this competition and to locate the CET. Experimental verification of modelling parameters considering melt flow is intended in the future work.