Materials · 2018 · 18 citations · 19 references
Natural SciencesMaterials EngineeringMaterials ScienceMetallic MaterialsMetallurgyPhase TransformationsAlloy SolidificationAlloysCrystallization ProcessesGrain Structure FormationMetalsMicrostructure EvolutionDynamic RecrystallizationGrain Morphology EvolutionGrain Size EvolutionGrain Structure EvolutionHomogenizationMagnesium AlloysMean Grain SizeMicrostructure
Repetitive upsetting extrusion (RUE) was applied to the as-homogenized Mg-12.0Gd-4.5Y-2Zn-0.4Zr (wt %) alloy at 773 K. The microstructure evolution of the alloy during RUE was investigated. The results indicated that almost all Mg₅(Gd,Y,Zn) phases and fine-lamellar long-period stacking-ordered (LPSO) phases were dissolved into the matrix after homogenization treatment at 793 K for 16 h. After one RUE pass, dynamic recrystallization (DRX) occurred. During subsequent RUE passes (from one to three passes), average volume fractions of DRXed grains increased from 43.9% to 65.8%, and that of fine-lamellar and block-shaped LPSO phases gradually decreased. All samples exhibited a typical bimodal microstructure consisting of some initial grains containing fine-lamellar LPSO phases, but consisting mostly of fine-DRXed grains with a mean grain size of 6 μm. Because of an increase in the accumulated strains, the coarse grains were substituted with fine-DRXed grains, the grains were gradually refined, and the microstructure distribution became more homogeneous.
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Yoshihito Kawamura, Kentaro Hayashi, Akihisa Inoue et al. · MATERIALS TRANSACTIONS · 2001 · 1.1K citations · Full text