Oxidation Kinetics and Oxide Scale Morphology of Fe-1.5Si Alloy

Abstract

Thermogravimetric analyzer (TGA) was used to simulate isothermal 60-min oxidation process of Fe-1.5Si alloy under air condition at 700°C-1150°C. Cross-sectional scale morphology and elemental distribution of the oxide layer were investigated by electron probe microanalysis (EPMA). At 700°C-1150°C the oxide scale is composed of external scale and internal Si precipitates zone. And Si-rich oxides can be detected in the inner parts of the outer oxide scale. It was found at 700-1000°C that oxidation mass gain curve obeys the parabolic law but at 1100-1150°C the relationship of mass gain and oxidation time is complex. The parabolic rate constant is lowered at 900-1000°C that should be related with thicker internal oxidation zone at 900°C and formation of the obvious Si-rich layer in external oxide scale at 1000°C.