The effects of cold-working and of subsequent annealing upon the H solubility of random solid solutions was considered. It was found that an enhanced H solubility in the dilute -phase after cold-working tended to decrease with increasing Ag content, and approached 0 at a Ag content of 40at%. The H solubility in Pd was known to increase after cold work, due to the interaction of dissolved H with the tensile stress fields of dislocations. However, recent findings had suggested that high dislocation densities in Pd-Ag alloys did not lead to a concomitant solubility enhancement. No explanation had been given for this observation, and the object of the present work was to determine whether the solubility enhancement of cold-worked Pd-Ni alloys increased or decreased with the atomic fraction of Ni. It was noted that substitutional Ni atoms tended to contract the Pd lattice; in contrast to the lattice expansion which resulted from substitutional Ag in Pd. A mechanism was proposed in which the larger Ag atoms and the smaller Ni atoms segregated to, or from, the tensile stress fields during cold-working of the binary alloys. This was expected to lead to changes in the fraction of Pd-rich sites that was available for H occupation in the tensile stressed regions.

S.Kishimoto, N.Yoshida, T.Hiratsuka, A.Nakano, T.Masui, T.B.Flanagan: Scripta Metallurgica et Materialia, 1994, 30[5], 643-7