Phase separation in titanium hydrides studied by small-angle neutron scattering

Various phases of titanium hydrides with differing hydrogen and deuterium content are studied by small-angle neutron scattering. The low temperature metastable χ phase produced by quenching under high pressure shows small, but pronounced scattering at liquid nitrogen temperature. At 140 K a very abrupt increase in the scattered intensity is detected, more than one order of magnitude for less than 30 s. The scattering from the room temperature (α+γ) phase is analysed by the fractal as well as the random two-phase model. The fit does not prove fractal behaviour of the α-Ti precipitates in the γ-TiH(D)₁ matrix. A good representation is obtained in a random two-phase model, giving about 50 and 60 angstrom correlation lengths, independently of the deuterium or hydrogen content. For the δ phase, only the asymptotic behaviour of the scattering curves is observed in the scattering vector range covered in the experiments.