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Microstructural effects and mechanism of bcc-hcp-bcc transformations in polycrystalline iron

Abstract : Cycling the α↔ε transformation in polycrystalline Fe is investigated using in situ x-ray diffraction under quasihydrostatic conditions. The forward α→ε transformation starts at 14±1 GPa and completes at 18±1 GPa while the reverse ε→α transformation starts at 10.5±0.5 GPa and completes at 6±1 GPa. The anomalous evolution of c/a ratios of ε-Fe measured at the onset of the α→ε transition in earlier studies is not observed. Microstructural features are consistent with a Burgers path for the transformation. The forward α→ε transformation is sensitive to the average and intergranular stresses, inducing a strong variant selection with the c axes of the new ε phase preferentially aligned perpendicular to compression and concentrated into one single orientation. Partial texture memory is observed as the sample returns to the α phase but, as transformation cycles go on, irreversible changes occur in the microstructures that are later fully induced by the cycles of phase transformations.
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Soumis le : lundi 14 septembre 2020 - 12:07:18
Dernière modification le : jeudi 9 juin 2022 - 08:20:08
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Sébastien Merkel, Ainhoa Lincot, Sylvain Petitgirard. Microstructural effects and mechanism of bcc-hcp-bcc transformations in polycrystalline iron. Physical Review B, American Physical Society, 2020, Physical Review B, 102, pp.104103. ⟨10.1103/PhysRevB.102.104103⟩. ⟨hal-02937692⟩



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