Investigation of dehydrogenation of Ti–V–Cr alloy by using in-situ neutron diffraction

Abstract

The hydride phase of Ti₅₀V₂₀Cr₃₀ alloy cast with 4 wt% of 7Zr+10Ni has been investigated. Pressure composition desorption isotherms were measured at 150 °C and 200 °C. These isotherms revealed same desorption of 1.5 wt% at 150 °C and 200 °C. The evolution of the crystal structure upon dehydrogenation was investigated by in-situ neutron diffraction. A sample was fully deuterated at room temperature under 2000 kPa pressure. Afterwards, the sample was heated from 120 °C to 266 °C under vacuum and neutron diffraction patterns were recorded as a function of temperature. It was found that the alloy started to desorb very quickly at 200 °C. The amount of fcc phase was monitored using the relative intensity of the fcc phase compared to a standard. At 266 °C only 10% hydride phase was seen, which was confirmed by X-ray diffraction. Besides the fcc phase, a minor aluminum phase due to the heating element was also observed in all patterns. Thermal expansion coefficient of Al and fcc phase were calculated. Using the aluminum peaks as reference, it was found that deuterium occupancy reflect the phase abundance of the fcc deuteride.