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Abstract: The transformation of titanium into several hydride phases has been studied by transmission electron microscopy at the surface of an acid-etched titanium substrate designed for biomedical applications. Four different orientation relationships have been found between face-centred cubic TiH2−ε (ε ≪1), face-centred tetragonal TiH and hexagonal close-packed Ti. A fast method based on the alignment of diffraction spots perpendicular to interfaces (Δg condition) is proposed, to account for the experimental orientation relationships and interface planes. Different paths leading to the formation of the two above-mentioned hydride phases have been thus identified. A mechanism of misfit relaxation has been observed and described. [Copyright &y& Elsevier]

The surface hydrides formed on commercial purity titanium (CP-Ti) and Ti–6Al–4V alloy having been electrolytically hydrogenated in 1 N aqueous sulfuric acid solution were identified to be δ-hydrides. Structure and composition of these δ-hydrides were affected by the thermal oxide films, the additive in the electrolyte, the applied current density and the operating period. The lattice constants of δ-hydrides (aδ) observed in this study range from 4.383 to 4.431 A˚ for CP-Ti and 4.293 to 4.308 A˚ for Ti–6Al–4V. The nonstoichiometric ratios, x, of δ-hydrides for CP-Ti after hydrogenated are not more than 1.84. X-ray diffractometry (XRD) gave aδ and x (indirectly from aδ–x curve) to characterize titanium hydrides. Glow discharge optical spectroscopy (GDOS) offered quantitative values such as maximum hydrogen diffusion depth (MHD), average hydrogen concentration (CA), specific hydrogen uptake (SHU), hydrogen uptake efficiency (HUE), coefficients of inhibiting performance (CIP) and hydrogen absorption rates to elucidate processing parameters on the hydrogenation behavior. [Copyright &y& Elsevier]