Deuterium driven phase transitions in the Ti3Al intermetallic Original Research Article

The phase changes in Ti3Al due to low temperature gas phase charging with deuterium have been determined as a function of deuterium concentration. The phases observed with increasing deuterium content were D in solid solution, a twinned βo phase with a DO19 structure, a large- and a fine-grained f.c.c. δ phase (δl and δf, respectively), and an amorphous phase. The decomposition of the deuterides was endothermic, with enthalpies of 66, 90 and 188 kJ/mol D for the βo, δl, and δf, and amorphous deuterides, respectively. The driving force for the generation of grain boundaries in the f.c.c. structure and the production of the amorphous phase with increasing deuterium concentration was provided by the difference in the site energies for deuterium in the lattice and the grain boundaries.