Experimental investigation and simulation assessment on fluidity and hot tearing susceptibility of Al-Li-Cu-X alloy: The role of microalloying elements

The meticulous exploration of castability, especially the fluidity and hot tearing susceptibility (HTS), assumes paramount significance in the fabrication of high-quality Al-Li-Cu alloys. In this work, the effect of microalloying elements such as Ti, Mg, Si, Zr, and Sc on the fluidity and HTS of the alloys was systematically investigated, and the significant improvement in fluidity and the reduction in HTS by the addition of these microalloying elements were identified. Comparative analyses with the Al-3Li-1.5Cu alloy reveal a significant increase of up to 45 % in fluidity and a remarkable reduction of up to 83 % in HTS with the addition of these microalloying elements. To unveil the underlying mechanisms, the experimental results were compared with the predictions derived from the CSC criterion, Kou's criterion, and a numerical simulation performed using ProCAST software. The analysis reveals a discrepancy between these predictions and the experimental outcomes, highlighting their limitations in capturing the nuanced effects of minor microalloying elements on fluidity and HTS. Subsequently, a detailed exploration of other influencing factors, including microstructural features, solidification interval, and various thermophysical parameters, was conducted, illuminating the corresponding mechanisms. These findings are expected to provide valuable insights into the fluidity and HTS of Al-Li-Cu-X alloys, thereby contributing to the application and advancement of cast Al-Li alloys.