HYDROGEN SOLUBILITY IN NIAL

The solubility of H in beta-NiAl has been measured by a quench and ana lyse technique over the temperature range 800-900-degrees-C and at pre ssures up to approximately 50 bar. This compound is noteworthy for the large concentration of vacancies on the Al-rich side of stoichiometry . The most notable features of the H solubility results are that the s toichiometric alloy has the lowest H solubility and that both the part ial molar relative enthalpy and standard relative entropy of H are low est at this composition. The observed compositional variation in the p artial standard entropy is much too large to be attributed to vibratio nal effects and a possible explanation in terms of configurational eff ects is proposed which involves the vacancies in the Al-rich alloys be ing available for H absorption.