Enhancing solidification cracking resistance in high-strength Al-Li alloys via strategic light rare earth alloying: An integrated experiment-simulation approach

Although Al-Li alloys possess advantages of low density and high stiffness, their severe hot cracking susceptibility (HCS) limits practical applications. Herein, we attempted to decrease HCS without sacrificing mechanical performance by replacing Sc with cost-effective light rare earth (LRE) elements. Results showed that the introduction of La, Ce, Nd, and Pr reduces the HCS to half that of the Base alloy due to grain refinement and melt purification. Finite element analysis (FEA) revealed that compared to elongated LRE phases characterized by high aspect ratios and interfacial curvature, blocky LRE phases with lower aspect ratios and interfacial curvature hinder crack propagation, leading to improved cracking resistance. Among the low-HCS variants, Pr-modified alloy shows remarkable yield strength of 398 MPa, exhibiting competitiveness compared to existing Sc-containing alloys. More importantly, Pr-modified alloy achieves a significant cost reduction of ∼27 %. The narrowed δʹ-Al₃Li precipitation free zone (PFZ) and the uniformly distributed fine T₁ precipitates contribute to the promising mechanical properties of Pr-modified alloy. First-principles calculations indicated that the higher vacancy binding energies of Nd and Pr atoms suppress δʹ-PFZ coarsening, while their doping increases the coarsening energy barrier of T₁ precipitates. These benefits mitigate stress concentration and enhance deformation compatibility.