Factors determining the compound phases formed by oxygen or nitrogen implantation in metals

Abstract

Oxygen or nitrogen implantation in a metal is well known to lead to oxides or nitrides, often in the form of precipitates. In some cases the phase formed is unambiguous in that there is either no phase stable with respect to O or N loss (e.g., Ag) or only one (e.g., Al). In other cases (e.g., Ti), however, two or more phases are possible in the sense of being stable with respect to O or N loss. We present a model based on the postulate that implanted O or N leads to precipitates which tend to be in q u a l i f i e d thermodynamic equilibrium with the metal. The qualifications are that a phase will fail to appear if subject to amorphization, O or N loss, or (for a phase the cations of which are crystallographically like the metal) randomization.