Partial decomposition of TiH2 studied in situ by energy-dispersive diffraction and ex situ by diffraction microtomography of hard X-ray synchrotron radiation

Phase transformations during partial decomposition of TiH2 powder were followed in situ by X-ray diffraction and thermoanalysis. During heating, endothermic H2 release regimes are correlated with the phase transformation sequence, in which the phases α + δ + β coexist because a hydrogen concentration gradient forms inside the particles. Cooling from 616 °C interrupts degassing close to the eutectoid composition, which suppresses the coexistence of α + δ + β. Microtomography indicates that the resulting microstructure comprises δ lamellae embedded in an α matrix in the proportions 31:69 (vol.%).