Hot tearing of cast aluminium alloys: A critical review

Cast aluminum (Al) alloys, owing to their low density and high specific strength, offer significant advantages in the fabrication of complex, large-scale, or monolithic structural components across civilian, defense, and military sectors that are weight-sensitive, including transportation, aerospace, and underwater weaponry. However, a substantial portion of these alloys often exhibit pronounced hot tearing susceptibility (HTS) during casting, which not only detrimentally affects the quality and efficiency of industrial production but also limits their further development in high-tech applications. Therefore, a comprehensive and profound understanding of hot tearing behavior in cast Al alloys is essential. This review first analyzes the formation mechanisms of hot tearing, encompassing strength theory, liquid film theory, intergranular bridging theory, solidification shrinkage compensation theory, and relevant models, as well as the key factors governing its occurrence, including alloy composition, grain structure, casting parameters, and inclusions. It then introduces current research methods, ranging from simple evaluation and physical parameter-based approaches to in situ observation and numerical simulation, followed by a summary of newly proposed hot tearing criteria. Finally, it discusses the remaining scientific challenges and outlines future research directions. Particular emphasis is placed on recent advances in the hot tearing of cast Al alloys over the past decade.