Influence of the C14 Ti35.4V32.3Fe32.3 Laves phase on the hydrogenation properties of the body-centered cubic compound Ti24.5V59.3Fe16.2

Bcc Ti24.5V59.3Fe16.2 alloys containing 10 and 30% of C14 Laves phase inclusions were prepared by induction melting followed by annealing at 1000 degrees C. X-ray powder diffraction and BSE microscopy confirmed the presence of the C14 Laves phase (average composition Ti35.4V32.3Fe32.3) embedded in the bcc matrix. The two end members of the series, the C14 Laves phase and the bcc Ti24.5V59.3Fe16.2 alloy, have very different hydrogenation behaviors. The C14 Laves phase does not absorb as much hydrogen as does the bcc phase. No equilibrium plateau and little hysteresis between absorption and desorption were observed at 25 degrees C for the C14 Laves on the PCI curves whereas those of the bcc sample present one equilibrium plateau and significant hysteresis between absorption and desorption. As a result, the absorption capacity and the length of the equilibrium plateau of the multiphase alloys decrease with the C14 Laves phase content. The hydrogenation properties of an as-cast bcc Ti24.5V59.3Fe16.2 sample were also investigated: the kinetics of the first hydrogenation is found to be slower and the plateau pressures higher for the as-cast alloy than for the annealed sample. (C) 2010 Elsevier B.V. All rights reserved.