Influence of lanthanum addition on microcracking behavior of dual-phase Mg-10Li-1.6Zn alloy: An in-situ investigation

The application prospects of dual-phase Mg-Li alloys (α-Mg (HCP)/β-Li (BCC)) are constrained by their low absolute strength and poorly understood deformation mechanisms. While rare earth (RE) alloying enhances deformability and strength either through solid solution or precipitate formation, the underlying mechanisms governing RE-modified deformation behavior remain inadequately characterized. Therefore, in the present work, a dual-phase Mg-Li alloy doped with 0.5 wt% lanthanum (La) was investigated regarding micro-crack initiation and propagation through in-situ tensile tests, with a focus on the interface precipitates. It is found that La addition resulted in refined grain size and blocked crack tips, leading to termination of crack propagation at α-Mg/β-Li interfaces and delayed fracture. Besides, La addition can also reduce strain localization and improve ductility by reducing the difference in hardness between α-Mg and β-Li phases. These findings provide insights into understanding formability and fracture behavior of La-doped Mg-Li alloys.