High content of solute elements (Zn, Mg, Cu) increases the hot tearing susceptibility resistance of Al-Zn-Mg-Cu alloys

Al-Zn-Mg-Cu alloy is widely used in aviation, automotive and other fields due to its advantages of high strength and low density. However, when produced through casting, these alloys tend to develop hot tears in the interdendritic regions during the final stages of solidification, where the remaining liquid phase is limited and liquid feeding is impeded at high solid fractions. In this study, aimed to heal the formed hot tears by increasing the proportion of the remaining liquid phase during the vulnerable final stages of solidification through the addition of equal proportions of alloying elements (Zn, Mg, Cu), thereby significantly reducing the alloy's hot tearing susceptibility (HTS). The results indicate that the ability of the remaining liquid phase in the later stages of solidification to fully heal the contraction pores between interdendritic liquid films is a critical factor in determining the alloy's propensity for hot tearing. Furthermore, a self-designed T-shaped test apparatus was employed to collect and quantitatively analyze the relationship between temperature, solidification contraction displacement, force, and the influence of adding different mass fractions of equal proportions of solute elements (Zn, Mg, Cu) on the alloy's HTS during solidification. The results of quantitative testing were verified using a macro-qualitative Constrained Rod Casting mold to analyze the alloy's HTS, with a high degree of consistency between the experimental results. This study reveals the relationship between alloy composition and hot tear resistance, providing both theoretical and experimental foundations for the design and application of Al-Zn-Mg-Cu alloys with excellent hot tear resistance.