High temperature studies of Fe-Mn-Al-C alloys with different manganese concentrations in air and nitrogen

The formation of AIN was studied using a series of Fe-Mn-Al-C alloys with manganese contents from 20 to 40 wt%. All investigations were carried out in air and nitrogen at 1000° C. The permeability (D _N N _N) of nitrogen in Fe-Mn-Al-C alloys was found to be a major factor influencing the formation of AIN precipitates which are always observed underneath the oxide scales of the specimen. The formation of AIN is related to the lower formation rate of Al₂O₃ and high permeability of nitrogen; therefore AIN can only be formed in those alloys with a higher manganese concentration because the specimens are treated in air and in pure nitrogen at 1000 C.