Achieving superior strength in high modulus Mg-Li matrix composites via rotary swaging with interfacial precipitation-induced strain compatibility

Abstract

The inherently low Young’s modulus and limited strength of Mg-Li alloys have long restricted their structural application potential. In this study, we developed a modulus-oriented TiB₂/LAZ532 composite via rotary swaging, integrating particle reinforcement, severe plastic deformation, and interface engineering. Rotary swaging refined the grain structure to the submicron scale and introduced a high density of dislocation substructures, thereby enabling substantial strength improvement. Meanwhile, Li(Al, Zn) precipitates were observed to form at TiB₂/matrix interfaces, as confirmed by TEM, phase-field simulations, FEA, and in-situ synchrotron XRD. These interfacial precipitates acted as middle layer reducing stress concentration and enhancing strain transfer across particle/matrix boundaries, thus achieving improved deformation compatibility. Owing to the dual contribution of matrix grain refinement/dislocation hardening and interfacial strain accommodation, the composite achieved an ultimate tensile strength of 455 MPa, Young’s modulus of 61 GPa, and a low density of 1.75 g/cm³. This unique combination of ultra-light weight and mechanical robustness highlights a functionally partitioned strengthening strategy, wherein reinforcement, processing, and interface design contribute complementary roles. The approach provides a generalizable pathway for designing next-generation lightweight Mg-Li structural materials.