Hydriding properties of mechanically alloyed icosahedral phase Ti45Zr38Ni17

The interaction with hydrogen was investigated for mechanochemically synthe sised icosahedral phase of the composition Ti45Zr38Ni17. It was demonstrate d that, unlike icosahedral phases of the same composition formed as a resul t of rapid quenching from melt or the annealing of alloys, hydriding of mec hanochemically synthesized icosahedral phase at 503 K is not preceded by an induction period and starts at a maximal rate even when hydrogen pressure is less than 0.1 MPa. A diagram of the composition of icosahedral phase ver sus equilibrium hydrogen pressure (P-T-C diagram) at 503 K was experimental ly obtained. Based on published data and the data obtained in our experimen ts, an assumption was made on the existence of two types of hydrogen positi ons in the icosahedral structure of the hydrogenated phase. The first type is more energetically bound hydrogen occupying the positions within the str ucture-forming icosahedral Bergman clusters. The concentration of such hydr ogen is approximately corresponding to the relation H/M=1.1. The second typ e is less bound hydrogen occupying the Linkages between these clusters as s olid solution. (C) 2001 Elsevier Science B.V. All rights reserved.