Investigation of the Kinetics of Oxidation of Vanadium Alloys

Abstract

According to the thermodynamic analysis of a V–O equilibrium system, the saturation of vanadium with oxygen is accompanied by the competing processes of formation and dissolution of VO oxide films followed by the penetration of oxygen in vanadium. In the case of oxidation of an active alloying element (5% Ti) in the bulk of the metal, the amount of oxygen accumulated in the V–5T–5Cr alloy can be almost twice as high as in unalloyed vanadium. For the description of oxidation, we propose a physicomathematical model taking into account the processes running on the metal–medium interface, chemical reactions of oxygen with alloying elements in the bulk of the metal, and accumulation of defects promoting the indicated physicochemical processes. This model differs from the well-known models based on the Fick equation for a given constant surface concentration of diffusant or a given law of variation of mass. Within the framework of the proposed model, we show that the influence of thermal cycling on the phase and structural state of alloys is positive. The use of barocycling is proposed and analytically justified. As compared with the isobaric mode, this procedure leads to significant changes in the distribution of oxygen and its concentration in vanadium alloys.