In situ radial X-ray diffraction study of texture and stress during phase transformations in bcc-, fcc- and hcp-iron up to 36 GPa and 1000 K Original Research Article

Using a newly developed experimental protocol based on externally heated diamond anvil cells, in situ stress and textures studies are performed on polycrystalline body-centered cubic-(α-), face-centered cubic-(γ-) and hexagonal close-packed-(ε-)Fe during plastic deformation up to 36 GPa and 1000 K. At 7 GPa and 973 K, α-Fe displays a texture attributed to dominant slip on image. Upon pressure increase up to 24 GPa at constant temperature, differential stress is shown to increase to 0.6 ± 0.1 GPa while Fe is transforming into γ-Fe and ε-Fe. Textures observed in γ-Fe are fully induced by phase transformation, with little effect of plastic deformation. Textures observed in ε-Fe are the result of phase transformation from γ-Fe combined with plastic deformation, with dominant basal image slip. The differential stress measured in ε-Fe is consistent with a shear strength of ∼1.9 GPa at 17 GPa and 300 K, with a temperature dependence of −0.003 GPa K−1 and a pressure dependence of 0.074.