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 degrees C a refined nanostructure (similar to 50 nm) in the alpha matrix resulted mainly from the formation of platelet beta(H) and delta 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 degrees C, the refined structure was eliminated, and the compressive yield stress and microhardness of Ti64 were lowered. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.