Achieving high strength-ductility synergy in a Mg97Y1Zn1Ho1 alloy via a nano-spaced long-period stacking-ordered phase

Abstract

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.

Keywords

• Mg wrought alloy
• Mechanical properties
• Long-period stacking-ordered (LPSO) phase
• Age-strengthening behavior
• Strengthening mechanism