材料期刊网

The effects of hydrogen treatment on the microstructure, lattice defects and mechanical properties of alpha-Ti were investigated by optical and electron microscopy, positron annihilation techniques and mechanical testing experiments. It is found that there are always two types of hydrides: the ordered f.c.t. gamma-hydride and f.c.c. delta-hydride, in hydrogenated alpha-Ti at room temperature. The observation of the former is a new result in the Ti-H system with relatively high hydrogen content ([H] approximate to 32.6 at.%). However, the amount of gamma-hydride appears to decrease when [H] is progressively increased. The amount of defects in the hydrogenated specimens is much more than in the dehydrogenated specimens. The defects generated by hydride formation are mainly dislocations and they become vacancy-like defects as the hydrogen content increases. The amount and morphology of the hydrides and the types of defects produce a significant effect on the microstructure of the matrix after dehydrogenation. Thus, by carefully controlling the hydrogen content one can improve the tensile and fatigue properties of alpha-Ti after dehydrogenation.