Influence of Mn on the solidification of Fe-Si-Al alloy for non-oriented electrical steel

Differential scanning calorimetry, thermodynamic calculations, and metallographic analyses were used for a determination of the solidification sequence in a Fe-2.42 %Si-0.5 %Al-0.94 %Mn alloy. For the prediction of the solidification process of the Fe-Si-Al-Mn alloy also a modified Scheil-Gulliver solidification model was used. According to the thermodynamic calculations the two-phase region in the selected Fe-Si-Al-Mn alloy is stable between 1,303 and 913 A degrees C. The highest mass-fraction of the gamma-phase is reached at 1,150 A degrees C. With decreasing temperature the austenite retransforms into ferrite. In the temperature range where the thermodynamic calculations predict the existence of the two-phase region in the DSC curves, weak thermal events were observed. A post-exposure metallographic analysis revealed that the substructures in the ferrite microstructure indicate the gamma A -> A I +/- phase transformation. This suggests consistency between the differential scanning calorimetry, the thermodynamic calculations, and the metallographic analyses.