Impurity-induced host-lattice vacancies in metals and interstitial alloys

The concentration of site Vacancies (v) is analysed as a function of the co ncentration of interstitial nonmetallic (X) atoms inside cubic-metal (Me) c rystals. Its increasing dependence is established. The a concentration may exceed the concentration of thermally activated vacancies in the 'pure' F.C .C.-Me at the same temperature and over a wide interval of X-concentration. Factors assisting the formation of such X-induced v are the following: (I) a strong repulsion of interstitial X-atoms and site Me-cations (2) a suffi cient solubility of X-atoms (or clustering that leads to their local accumu lation in interstices). On the contrary, an application of the pressure dec reases the content of the impurity-induced a. An influence of such a on ins tability of alloys, that may lead to their polymorphic transformations, is considered. A monotonously increasing dependence is established for the a c oncentration as a function of H concentration in F.C.C.-Fe. The gamma*-phas e of F.C.C.-Fe-H is expected to be enriched with vacancies at high H-doping levels. For instance, that is important as a precursor effect of spontaneo us deformation ('quasi-liquid state') near the F.C.C. to B.C.C.-Fe transfor mation in H atmosphere. (C) 1999 International Association for Hydrogen Ene rgy. Published by Elsevier Science Ltd. All rights reserved.