New determination method of hydrogen diffusivity in titanium-hydrides by means of diffraction-enhanced X-ray imaging method

Abstract

The X-ray refraction imaging technique, diffraction-enhanced X-ray imaging (DEI) method was applied to determine the .hydrogen diffusivity in titanium-hydride. Hydride was formed on titanium surface by electrolytic-charging at room temperature for 6, 12, 18, 24 and 48 h. The specimen was cut into a 1-mm thick slice for cross-sectional observation. Hydride layer was observed by DEI method as a thick black or white line parallel to the surface. Hydride distribution caused by hydrogen diffusion from the surface was calculated using assumed hydrogen diffusivity and a solution of diffusion equation. And the results were converted to the intensity profile of refraction images of the hydride using the measured rocking curve from an analyzer. The intensity profile was compared with that obtained from the photographs and fitted diffusivity was decided by trial and error. The obtained diffusion coefficient of hydrogen in titanium-hydride, 3.6 x 1 0' 15 m' 2 /s, was slightly larger than the value obtained by internal friction at room temperature.