Effect of substitution on FCC and BCC hydride phase formation in the TiCr2-H2 system

Phase transformations of TiCr1.8, ZrCr2, Ti0.9Zr0.1Cr1.8, Ti0.7Zr0.3Cr1.8 and TiCr1.7Fe0.1 intermetallic compounds during their interaction with hydrogen at pressures from 1 to 200 MPa and temperatures of 195 and 295 K are studied. Formation of three types of hydride phases are stated by X-ray diffraction method: (I) hexagonal Laves phase preserving the MgZn2 structure of the initial intermetallic, (II) F.C.C. phase of CaF2 structure type which can be considered as a solid solution in the pseudobinary TiH2-CrH2 system and (III) B.C.C. phase with W-structure type-high temperature beta solution in the metallic Ti-Cr system stabilized by hydrogen. It was shown that partial substitution of titanium by zirconium up to 30% did not change the general scheme of phase transformations, while the addition of iron suppressed the formation of phases (II) and (III) in all experimental pressure and temperature ranges. The conditions of formation, X-ray parameters and thermal stability have been determined for synthesized hydride phases in the TiCr2-H-2 and substituted systems. (C) 1999 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.