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

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-(alpha-), face-centered cubic-(gamma-) and hexagonal close-packed-(epsilon-)Fe during plastic deformation up to 36 GPa and 1000 K. At 7 GPa and 973 K, alpha-Fe displays a texture attributed to dominant slip on {1 1 0}. 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 gamma-Fe and epsilon-Fe. Textures observed in gamma-Fe are fully induced by phase transformation, with little effect of plastic deformation. Textures observed in e-Fe are the result of phase transformation from gamma-Fe combined with plastic deformation, with dominant basal (0 0 0 1)< 1 1 (2) over bar 0 > slip. The differential stress measured in epsilon-Fe is consistent with a shear strength of similar to 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.