Keijiro Nakasa1 and Jianping Liu2
1Department of Mechanical Engineering, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima
An X-ray diffraction analysis was carried out both for bowed-specimen and ball-indented specimen, which were cathodically hydrogen charged in sulfuric acid solution under a current density of 3000 A/m2, to investigate the effect of tensile and compressive stresses on the behavior of hydride formation in Ti-6Al-4V alloy.
For the bowed-specimen, γ-hydride (fcc) was formed more easily under tensile stress than under compressive stress. The formation of δ-hydride (fct), on the other hand, was only slightly easier under tensile stress than under compressive stress. The γ-hydride formed under tensile stress was decomposed to the α-titanum phase when the stress was reversed to compression, leaving the δ-hydride unchanged. However, the γ-and δ-hydrides formed under compressive stress did not change when the stress was reversed to tension. For the ball-indented specimen, the amount of γ-and δ-hydrides showed a minimum in the center of indentation with the largest compressive stress. Besides, the indentation on a plate specimen after hydrogen charging decreased the γ-hydride but increased the δ-hydride. The effect of stress on the hydride formation and decomposition appear to be explained by the habit planes of hydride relative to α-lattice, and the expansion during hydride formation.
hydride formation, stress effect, Ti-6Al-4V alloy, hydrogen charging, X-ray analysis, habit plane
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