Predicting the transition from internal to external oxidation of alloys using an extended Wagner model

摘要: Abstract Leblond [Oxid. Metals 75 (2011) 93–101] recently estimated the conditions governing transition from internal to external oxidation of alloys using a variant Wagnerʼs [Z. Elektrochem. 63 (1959) 772–782] model incorporating possible role oxides as diffusion barriers, through heuristic dependence coefficient oxygen upon their local volume fraction. But crudeness formula adopted made prediction onset only qualitative. A more accurate is derived here by thermal analogy and finite element computations reduction conductivity generated nonconducting, or less flat obstacles. The extended Wagner this leads “critical” fraction corresponding oxidation, depending on “aspect ratio” oxides. predicted value in acceptable agreement with that measured Rapp [Acta Metall. 9 (1961) 730–741] for Ag–In system, reasonable postulated aspect ratio.