The Effect of Solute Suppressed Nucleation Effect and Latent Heat on the Grain Refinement of Cast Aluminum Alloy

Grain refinement is the key to developing high-quality cast aluminum alloys. Based on the solute conservation theory and dendritic growth kinetics model, this paper developed a cellular automaton (CA) numerical model and fully considered the complex evolutionary processes, such as nucleation particle characteristics, nucleation-growth process, dynamic solute diffusion, and latent heat release during the solidification process of aluminum alloys. The CA model was used to quantify the role of solidification latent heat and solute diffusion in the grain nucleation process. The influence of solute suppressed nucleation (SSN) and solidification latent heat on the grain refinement effect of aluminum alloys are systematically studied. The results showed that when only considering the SSN effect, with the increase of nucleation density, the refinement efficiency decreases from 81.2 to 45.98 pct, and the decrease gradually decreases. This was mainly due to the increase of number of particles in the solute diffusion layer. The grain separation distance (GSD) became smaller than the size of the invisible nucleus region, reducing in the nucleation efficiency of the particles there. When the model further considered the effect of latent heat, the refinement efficiency was sharply dropped to 7 pct. The re-glow phenomenon caused by latent heat release limited the possibility of nucleation of small-sized particles and particles located in the SSN zone. Therefore, latent heat was fond to be the main factor restricting grain refinement.