Recent advances in grain refinement of aluminum alloys: Nucleant particles and solute effects
Qiuju Zheng, Jing Wu, Ruxin Cao, Tian Chen, Wenhou Wei, Shoufeng Yang
Abstract
All metallic materials begin their life through solidification. A detailed understanding of solidification phenomena is critical for controlling microstructural evolution and enhancing material performance. This state-of-the-art review presents the recent developments in grain refinement during the solidification processing of aluminum alloys, focusing on the two primary interrelated factors governing grain size: nucleant particles and solute elements. The review commences with an overview of established grain refinement theories, including heterogeneous nucleation, constitutional undercooling and the interdependence theory (Section 2). The subsequent review emphasizes the effect of key factors influencing grain refinement performance: nucleant particles potency, size distribution, kinetic behaviors and solute elements (Section 3). A comprehensive discussion then covers the recent progress in novel grain refiners, their efficiency and grain refinement mechanisms under the near-equilibrium solidification (conventional casting, Al-Ti-B-X refines) and rapid solidification (additive manufacturing, in-situ Al 3 X phases and ex-situ nanoparticles). The article concludes by outlining major findings and presenting an outlook on future development directions including quality control and evaluation, intelligent grain refiner design, standardized grain refinement theories and multifunctional agent development. This review aims to provide holistic insights into grain refinement for conventionally cast and additive manufactured Al alloys, thereby controlling the microstructure and advancing the development of high-performance of Al alloys.