The internal oxidation of two-phase binary alloys under low oxidant pressures

The main features of the internal oxidation in two-phase binary alloys are examined for insignificant and important diffusion of the most-reactive component and are compared with the behavior of corresponding single-phase systems. It is shown that two-phase alloys may have two different types of internal oxidation, one of which is similar to that of the single-phase alloys (classical type), producing a uniform distribution of small oxide particles in the zone of internal oxidation, while another is typical of two-phase systems and involves the in situ conversion of the most-reactive component into its oxide. It is also shown that, under the same values of all the relevant parameters, the classical internal oxidation of two-phase alloys involves faster kinetics and smaller degrees of enrichment of the most-reactive component in the zone of internal oxidation than for single-phase alloys. As a consequence of this, the transition to the external oxidation of the most-reactive component in these systems involves higher overall concentrations of the most-reactive component than in corresponding single-phase alloys.