Uniaxial deformation experiments were carried out using a D111-type apparatus installed on a beamline NE7A at PF-AR, KEK, and a deformation-DIA apparatus installed on a beamline BL04B1 at SPring-8. Using a pre-sintered iron rod as a starting material, deformation experiments were carried out at pressures of 16.9-22.6 GPa and temperatures of 423-873 K where hcp-iron stably exists. The stress and strain of the sample during deformation were determined based on two-dimensional X-ray diffraction and X-radiography, respectively, using a monochromatized synchrotron X-ray.
The results showed that the dominant deformation mechanism in hcp-iron changes depending on the temperature, with power-law dislocation creep and low-temperature creep being most important above and below ~800 K, respectively. Based on extrapolation of these experimental results we estimate the inner core viscosity to be ≥ 1019 Pa s,suggesting that the equatorial growth or translation mode model is the dominant geodynamical mechanism in the Earth’s inner core.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022JB026165