Population dynamics behaviors of TiC and their effect on grain refinement in Al–Ti–C refiners: Growth, agglomeration, nucleation and precipitation

The refining performance of Al–Ti–C grain refiners is strongly influenced by the population dynamics behaviors governing the nucleation surface, number density, and average particle size of TiC. This study, combining experimental observations and theoretical studies, investigates the population behaviors, including growth, agglomeration, nucleation, and precipitation, of TiC particles and their effects on grain refinement. Results indicate that four distinct forms of agglomeration—vertex joint, edge joint, interpenetrating crystal, and surface adhesion—each driven by specific dynamic factors including surface energy and twin, lead to the deterioration of TiC (111) nucleation planes, resulting in diminished refining performance. The established agglomeration-coupled population dynamics model reveals reflects an increase in the average particle size of TiC, while the number density and volume fraction gradually decline, during isothermal insulation. Additionally, agglomeration-driven accelerated precipitation removes active nucleation sites from the melt, further reducing refining performance. These insights into population dynamics behaviors of TiC underscore the importance of carefully controlling these factors to optimize the refining performance of Al–Ti–C refiners.