Abstract The ability to accurately predict microstructural evolution in response to metallic alloy composition and thermal processing parameters is of critical importance in preventing defects and maximising sustainability in advanced liquid metal processing manufacturing, e.g. casting, welding, and additive manufacturing. Sophisticated solidification models are used widely in industry to optimise mould designs and processing parameters. To ensure validity of simulation predictions, similarly sophisticated solidification experiments are required. Since its development, real-time in situ X-ray radiography of solidification has become the benchmark for solidification experimentation, providing significant insight into nucleation, primary phase evolution, solutal rejection, soft and hard impingement, and isothermal transformations. The compact nature of lab-based X-ray diagnostic equipment and solidification furnaces have enabled metal alloy solidification observation in real time under microgravity conditions. One such experiment was performed on board the MASER 13 sounding rocket showing, for the first time, complete isothermal equiaxed solidification metallic alloy in microgravity. In this work, mesoscale Front Tracking (FT) was used to simulate that microgravity experiment on the grain-refined Al-20wt.%Cu disc-shaped sample. Experimental data was used to initialise the FT algorithm with grain envelope development predicted based on the applied cooling rate. Latent heat release during solidification was shown to have a negligible impact on solidification overall, owing to the small volume of metal and the relatively low cooling rate. Soft impingement, i.e. solutal awareness, of neighbouring grains was shown to be the dominant mode of primary dendrite growth restriction and inoculant particle poisoning.
Murphy et al. (Mon,) studied this question.