PHASE-SEPARATION IN TITANIUM HYDRIDES STUDIED BY SMALL-ANGLE NEUTRON-SCATTERING

Various phases of titanium hydrides with differing hydrogen and deuter ium content are studied by small-angle neutron scattering. The low tem perature metastable X 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 detecte d, more than one order of magnitude for less than 30 s. The scattering from the room temperature (alpha+gamma) phase is analysed of the alph a-Ti precipitates in the gamma-TiH(D)1 matrix. A good representation i s obtained in a random two-phase model, giving about 50 and 60 angstro m correlation lengths, independently of the deuterium or hydrogen cont ent. For the delta phase, only the asymptotic behaviour of the scatter ing curves is observed in the scattering vector range covered in the e xperiments.