The oxidation and carburization of FeMnAl alloys in a carbon-containing atmosphere

Abstract The morphology and reaction process of two austenitic FeMnAl alloys in the carbonaceous atmosphere were studied in this work. The austenitic FeMnAl alloys is internally oxidized and carburized in a carbon monoxide atmosphere in the temperature range from 900 to 1070 °C. The internal oxide is a mixture of MnAl 2 O 4 and Al 2 O 3 , and the carbide is perovskite carbide with the formula (Fe,Mn) 3 AlC 0.5 . Oxidation and carburization of studied FeMnAl alloys in the CO atmosphere were proposed to occur in the sequence of CO dissociation, transportation of C and O atoms, internal oxidation, carbide formation and decomposition. During internal oxidation, Al 2 O 3 was formed first by selective oxidation of Al. The Al 2 O 3 particle then acted as the nucleus of the spinel oxide formation. MnAl 2 O 4 grew from the Al 2 O 3 particles to the finally observed morphology as the oxygen content around the Al 2 O 3 particle became favourable for the formation of MnAl 2 O 4 . The carbide was formed as the C content in the matrix exceeded the solubility of the alloy and it decomposed as the oxygen content around the carbide higher than the equilibrium oxygen content of Al 2 O 3 .