Scale morphologies and compositions of an iron-manganese-aluminum-silicon alloy oxidated at high temperatures

Abstract

An Fe-34Mn-7.3Al-1.4Si alloy was prepared by vacuum induction melting. The cylindrical-shaped ingots were first homogenized at 1200 °C, forged at 1000 °C, cut and cold-rolled, followed by a homogenization heat treatment at 1000 °C, for 1 hour. The samples were submitted to oxidation tests in air at temperatures ranging from 600 to 1200 °C, for times between 1 and 45 hours. The morphologies of the oxide scales were studied by X-ray diffraction, optical and scanning electron microscopy with EDS facilities. The results showed a good oxidation resistance between 600 and 900 °C and poor oxidation resistance at temperatures above 1000 °C. The presence of a second phase after oxidation was responsible for the poor oxidation resistance. Three classes of oxides of aluminum, manganese and iron were identified and established according to the oxidation conditions. The levels of aluminum required to form protective scales as a function of the oxidation temperature and time were discussed.