An investigation of some palladium-titanium and some palladium-titanium-hydrogen alloys

Abstract

The room temperature lattice spacings (of both powdered and solid samples), microhardness values and magnetic susceptibilities of some Pd-Ti alloys in the composition range 0−-30% Ti∗ have been determined in the present investigation. The lattice spacings of the solid samples indicate a small progressive contraction of the palladium lattice on adding titanium, apart from the composition range 7− -14.5% Ti where the spacing is invariant with composition. It is proposed that this plateau region in the spacing-composition variation is due to the compensatory effects of ordering and of progressive titanium additions. The variation of microhardness with titanium content can be correlated with the corresponding variation in the lattice spacings and both can be interpreted in terms of the appearance of short range order (SRO) and eventually long range order (LRO) in these alloys. The magnetic susceptibility measurements for the alloys up to about 9% Ti indicate an effective valency of 4.0 for the titanium atoms in solution in palladium. Alloys in the composition range 0−-8.7% Ti were gaseously charged with hydrogen and the results indicate that the equilibrium pressures for the hydrogen solid solutions increase rapidly with Ti content and are considerably higher than those for the equivalent Pd-Ce solid solution alloys. On hydrogenation the alloys become harder; this can be attributed to the influence of hydrogen on the atomic mismatch factor and, at certain compositions, to the additional effect of transformation hardening due to the α/β miscibility gap.