The effect of aluminium depletion on the oxidation behaviour of FeCrAl foils

In thin FeCrAl foils, the formation of a chromia layer within or underneath the alumina layer has been observed after consumption of the aluminium from the alloy. For Aluchrom I SE, the growth law of the alumina-forming step has been evaluated and an activation energy for oxygen diffusion of 383 +/- 36 kJ mol(-1) has been determined. For the growth mechanism of the chromia layer, three models are introduced and discussed. In agreement with a model proposed by H. E. Evans, the measurements of the aluminium content resulted in complete aluminium consumption before the beginning of chromia formation. Because of strong deformation of the thin samples during oxidation, a model is proposed to calculate the alloy thickness based on the amount of aluminium consumption. From a comparison of these calculated values with the measured thicknesses, the elongation of the sample due to creep processes could be determined.