Effect of Al Content on Inclusions in Fe-15Mn-xAl-C Low-Density Steel

Three experiments of Fe-15Mn-xAl-C (x=1, 3, 5) low-density steel with different Al contents are carried out, and the characteristics of inclusions are observed through field-emission scanning electron microscopy. The results show that the types of inclusions in the three samples are almost the same, mainly Al2O3, AlN, MnS, TiN, Al2O3-MnS, AlN-MnS, TiN-MnS, and Al2O3-AlN-MnS. The number percentage of Al2O3 decreases, while the number percentage of AlN increases with the increase of Al content in the three samples. As the Al content increases, the number of inclusions between 1 and 5 mu m decreases, while the number between 5 and 10 mu m increases. FactSage8.2 software calculation shows that an increase in Al content leads to an increase in the liquidus and a decrease in the solidus of the steel; at the same time, it causes the austenite region to narrow and expands the ferrite region. The change in the solidification route leads to a delay in the solidification fraction of AlN, MnS, and TiN inclusions precipitation. At last, the 2D mismatch theory shows that the mismatch degrees of Al2O3/MnS, AlN/MnS, TiN/MnS, and AlN/Al2O3 are 8.41%, 8.94%, 11.65%, and 11.66%, respectively.