Synergistic effect of in situ TiB₂ particle and Ti solute on fluidity and hot tearing susceptibility of Al–Li–Cu–X alloy

The quality of Al–Li castings is significantly influenced by fluidity and hot tearing susceptibility (HTS), underscoring the importance of comprehending castability and the related influencing mechanisms. Hence, this work systematically explores the synergistic effect of in situ TiB₂ particles and Ti solute on fluidity and HTS of the Al–Li alloys. The addition of Ti solutes or in situ TiB₂ particles yields a discernible improvement in both the fluidity and HTS of the Al–Li alloys. Furthermore, their combined addition further enhances fluidity and reduces HTS, resulting in a significant 67.3% enhancement and a remarkable 59.1% decrease, respectively. To elucidate these underlying influencing mechanisms, experimental results were compared with predictions derived from numerical simulation using ProCAST software, alongside assessments based on the CSC and Kou’s criteria. Numerical simulations closely align with experimental results. However, the CSC criterion and Kou’s criterion exhibit discrepancies when compared to experimental observations, highlighting their limitations in capturing the nuanced effects of minor Ti addition or TiB₂ particles on fluidity and HTS. Therefore, a comprehensive exploration of other influencing factors, encompassing microstructural features, solidification interval, and diverse thermophysical parameters, was thoroughly examined to uncover the influencing mechanisms. These outcomes are poised to offer profound insights into the fluidity and HTS of Al–Li alloys, thereby advancing the utilization and progression of cast Al–Li alloy applications.