Variation of structure and mechanical properties of Ti–6Al–4V with isothermal hydrogenation treatment

Grain refinement of Ti–6Al–4V (Ti64) was achieved by means of nucleation and growth of hydride phases associated with repeated isothermal hydrogenation (RIH). With a hydrogen loading of 0.7 H/M at 600 °C, a refined nanostructure (∼50 nm) in the α matrix resulted mainly from the formation of platelet βH and δ by the RIH treatment. The first cycle of RIH significantly increased the hardness and yield compressive stress, but further RIH cycling became less effective. For RIH with a hydrogen loading of 0.5 H/M at 750 °C, the refined structure was eliminated, and the compressive yield stress and microhardness of Ti64 were lowered.