Dislocation strengthening, as one of the methods to simultaneously enhance the room temperature strength and ductility of alloys, does not achieve the desired strengthening and plasticity effect during elevated-temperature deformation. Here, we report a novel strategy to boost the dislocation multiplication and accumulation during deformation at elevated temperatures through dynamic strain aging (DSA). With the introduction of the rare-earth element Ho in Mg-Y-Zn alloy, Ho atoms diffuse toward dislocations during deformation at elevated temperatures, provoking the DSA effect, which increases the dislocation density significantly via the interactions of mobile dislocations and Ho atoms. The resulting alloy achieves a great enhancement of dislocation hardening and obtains the dual benefits of high strength and good ductility simultaneously at high homologous temperatures. The present work provides an effective strategy to enhancing the strength and ductility for elevated-temperature materials.

Achieving high strength in Mg alloys is usually accompanied by ductility loss. Here, a novel Mg₉₇Y₁Zn₁Ho₁ at.% alloy with a yield strength of 403 MPa and an elongation of 10% is developed. The strength-ductility synergy is obtained by a comprehensive strategy, including a lamella bimodal microstructure design and the introduction of nano-spaced solute-segregated 14H long-period stacking-ordered phase (14H LPSO phase) through rare-earth Ho alloying. The lamella bimodal microstructure consists of elongated un-recrystallized (un-DRXed) coarse grains and fine dynamically-recrystallized grains (DRXed regions). The nano-spaced solute-segregated 14H LPSO phase is distributed in DRXed regions. The outstanding yield strength is mainly contributed by grain-boundary strengthening, 18R LPSO strengthening, and fiber-like reinforcement strengthening from the nano-spaced 14H LPSO phase. The high elongation is due primarily to the combined effects of the bimodal and lamellar microstructures through enhancing the work-hardening capability.