Influence of vanadium on hydrogen diffusion and phase constitution in Ti–H

The nuclear magnetic resonance method is used to investigate the influence of small amounts of vanadium on the phase constitution and hydrogen diffusion in Ti‐H. The temperature dependence of the proton spin‐lattice relaxation time is obtained at 27 MHz for samples representative of the α, β and γ phases of the system. The influence of V on the Ti‐H phase diagram is presented. The probable location of hydrogen in the β phase is found to be the octahedral Oz sites of the b.c.c. lattice. It is determined that the hydrogen diffusion activation energy E_a in the β phase of Ti‐H containing about 4% V is (2.3 ± 0.1) kcal/mole which is about 1/3 of that obtained for the vanadium free case. This amount of vanadium has very little effect on the activation energy in the α phase where it is found that E_a = (11.5 ± 0.8) kcal/mole. It is also found that vanadium decreases the hydrogen diffusion activation energy in the γ phase and causes a non‐linearity in the Arrhenius plot. The lower temperature activation energies are found to be 11.2, 9.7, and 9.0 kcal/mole for TiH_1.70 + 1.03% V, TiH_1.74 + 2.59% V, and TiH_1.63 + 4.36% V, respectively, where the vanadium percentage is the metal percentage prior to the introduction of hydrogen. The consequences of these effects on the problem of hydrogen embrittlement is discussed.