Effect of solutes on grain refinement

Grain refinement not only enhances the mechanical performance of as-cast metallic materials but also provides an effective mechanism for controlling cast defects, such as macro-segregation, porosity and coarse second phase particles. Therefore, understanding grain refinement of alloys with different solute additions is of both theoretical and practical importance. Although extensive research has been carried out over many decades and significant progress has been made on the subject, such historical research has not delivered the desirable scientific understanding, and many critical questions remain open. Adopting a hybrid approach between review and overview, in this paper, we firstly provide a brief review on the historical research on the solute effect on grain refinement in the literature, then present the recent advances in the understanding of the subject in a holistic manner, and finally offer a summary of the factors that hindered progress in the past, key advances made in recent years and some suggestions for future research directions.