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Free keywords:
Dynamic recrystallization; Gadolinium alloys; Grain boundaries; Grain size and shape; High strength alloys; Magnesium alloys; Precipitation (chemical); Upsetting (forming); Yield stress; Yttrium alloys; Zircaloy, Bi-modal grain structure; Forming temperature; Grain boundary strengthening; Heterogeneous deformation; Mg-gd-y-zn-zr alloys; Microstructure and properties; Precipitation strengthening; Ultrahigh strength, Zinc alloys
Abstract:
An ultrahigh strength Mg-10Gd-4Y-1.5Zn-0.5Zr alloy was prepared by the combined process of extrusion, pack-forging and aging treatment. The resultant alloy possesses a bimodal grain structure, a high number density of nanoprecipitates and long period stacking ordered (LPSO)/stacking faults (SFs). Numerous dispersive precipitates formed after the aging treatment due to the high number density of dislocations induced by pack-forging at low forming temperatures. The additional compression stress benefited from the pack-forging accelerates the dynamic dissolution of the LPSO phase and precipitation of SFs. Heterogeneous deformation induced (HDI) strengthening is achieved from the bimodal grain structure and different types of dynamic recrystallization (DRXed) grains, which significantly enhance the yield strength. Besides, grain-boundary strengthening and precipitation strengthening contribute to the high yield strength as well. © 2020
