Ultra-high specific strength of Mg–Li alloy via rotary swaging

Ultralight Mg–Li alloys demonstrate significant potential for critical structural applications, yet their widespread adoption has been constrained by insufficient specific strength. Through multi-pass rotary swaging processing, we significantly enhance the mechanical properties of Mg–4Li alloy, achieving an exceptional specific strength of 214 kN•m/kg—far surpassing those of conventional binary Mg–Li alloys—alongside a yield strength of 277 MPa and a tensile strength of 343 MPa. This remarkable improvement stems from the formation of a refined nanograin structure. Comprehensive microstructural analysis identifies two primary refinement mechanisms: (1) dislocation-mediated grain subdivision and (2) twin-twin intersection-induced grain refinement, which collectively contribute to the development of nanocrystalline domains. The achieved grain refinement efficiency demonstrates rotary swaging's unique capability in processing hard-to-refine Mg alloys, overcoming the intrinsic limitations of conventional thermo-mechanical methods. This breakthrough suggests new possibilities for developing ultrahigh-strength Mg–Li systems. • Introduced a method of rotary swaging which suggesting new possibilities for developing ultrahigh-strength Mg–Li systems. •Achieved an exceptional specific strength of 214 kN m/kg, far surpassing conventional binary Mg–Li alloys. •Found the dislocation-mediated grain subdivision and twin-twin intersection-induced grain refinement mechanism.