An Investigation of Some Palladium-Titanium Alloys

Abstract

The room temperature lattice spacings, micro-hardness values and magnetic susceptibilities of some Pd-Ti alloys in the composition range 0 to 30%Ti* have been determined in the present investigation. Differences in the lattice spacings of powdered and solid specimens in the early composition range have been attributed to the absorption of hydrogen by the powdered material. The lattice spacings of the solid samples indicate a progressive contraction of the palladium lattice on adding titanium, apart from the composition range from 7 to 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 compensating effects of ordering and of progressive titanium additions. Superlattice reflections indicative of a defect-type, Cu3Au structure, have been observed at titanium contents > 16% and there is a linear variation of spacing with composition in the range 14.5 to 23%Ti. It is proposed that the behaviour of these Pd-Ti alloys is similar to that observed in the Pd-Sc system. There is tentative evidence for structural instability in the hexagonal Pd3Ti phase at elevated temperatures. The variation of micro-hardness 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 (S.R.O.) and eventually long range order (L.R.0.) in these alloys. The magnetic susceptibility measurements are in good agreement with a previous study and indicate an effective valency of 4.0 for the titanium atoms in solution in palladium.