Effects of hydrogen on the mechanical properties of Ti-Al-Zr alloy

The distribution and structure of hydrides in the alloy and the effects of hydrogen on the mechanical properties of the alloy have been studied using electron microscope and mechanical test systems. The results indicated that the hydrides in Ti-Al-Zr alloy formed as platelets and had the fcc delta-structure with lattice parameter a = 0.438 nm. The alloy showed different sensitivities to the hydrogen embrittlement in tensile tests and impact tests. Hydrogen and formed hydrides induced hardening and caused slight loss in the ductility examined in the tensile tests. However, the impact toughness decreased dramatically with increasing hydrogen concentrations. indicated that the critical hydrogen concentration required to embrittle the alloy might be lower than 700 wppm. The difference in ductility measured in the two test methods were thought being resulted from the stress assisted hydrogen diffusion and the hydride formation in the impact specimen and in the necking area of a tensile specimen. The results have been discussed extensively. (C) 2004 Elsevier B.V. All rights reserved.