The mechanism of hydride formation during electrochemical hydrogen charging of Ti–6Al–4V

Abstract

The present work studies experimentally the hydrogen uptake and hydride formation in duplex Ti–6Al–4V. Hydrogen is introduced by electrochemical hydrogen charging at room temperature. The effect of the applied charging conditions is evaluated considering the effect of the charging duration and charging current density. Moderate charging conditions induce solute hydrogen in the lattice, resulting in lattice strains, as revealed by X-ray diffraction. More severe hydrogen exposure results in the formation of titanium hydrides when the hydrogen concentration exceeds the solubility limit of the Ti-α phase, as verified by a combined characterization with X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, and hydrogen melt extraction. A progressive mechanism of hydride formation upon increasing hydrogen content is proposed as the charging conditions clearly influence the hydrogen distribution and hydride formation in the material. Controlling the electrochemical hydrogen charging conditions enables to further understand the role of hydrogen and hydrides in hydrogen-induced failure mechanisms, as well as it offers opportunities for sustainable thermohydrogen processing of titanium.