Abstract
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 β H 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. © 2008 Acta Materialia Inc.