Application of Nuclear Reaction Analysis to Stress-Induced Hydrogen Migration in Titanium

The role of hydrogen as a cause of embrittlement and crack initiation in titanium alloys has long been recognized. However, direct experimental observation of the transport and accumulation of hydrogen in regions of high stress in titanium alloys has been sparse. We have applied the method of nuclear reaction analysis to the investigation of stress-induced hydrogen redistribution in Ti alloys. A 4 MV Van de Graaff accelerator is used to produce a high energy 7Li ion beam to induce the 1H(7Li, γ)8Be reaction. The measured gamma ray emission rate is proportional to the hydrogen concentration in the sample. In-situ measurements of the extent of hydrogen concentration change have been made in ß-phase Ti-13Mn and Ti-31V alloys to which a uniaxial stress gradient has been applied. The diffusivity of hydrogen in ß-phase Ti alloys has been determined by measuring the rate of change of hydrogen content following a reversal of the stress gradient in hydrogen charged specimens.