Solution of hydrogen in cold-worked Pd-Ni, Pd-Pt, and Pd-Ni-Ag alloys

The effect of cold-working on hydrogen solubilities in the dilute region (α phase) has been investigated for Pd1-xNix(x≤0.2), Pd1-xPtx(x≤0.19), and Pd1-xNi(1/2)xAg(1/2)x(x≤0.2) alloys by measuring pressure-composition isotherms between 273 and 348 K. The enhancement of hydrogen solubility in Pd-Ni alloys resulting from dislocation-hydrogen interaction tends to increase with increasing Ni content, in contrast to the case of Pd-Ag and Pd-Au alloys. On the other hand, the solubility enhancements in Pd-Pt and Pd-Ni-Ag alloys did not change significantly with alloying metal contents. These results can be qualitatively explained by the interactions between the alloying elements with different sizes and the stress fields of dislocations. The hydrogen trapping at defects such as vacancies was also predicted from the observation of the initial region of the isotherms for cold-worked alloys. It was found that the extent of pressure hysteresis in the isotherm for Pd0.9Ni0.1 alloy which has been initially cold-worked is less than for the well-annealed alloy and in the case of Pd0.85Ni0.075Ag0.075 alloy the hysteresis disappears completely.