Effect of aluminium content on the formation of inclusions in Fe–5Mn–<i>x</i>Al steels

Abstract

The effect of Al content on the characteristics and formation of inclusions in the light-weight Fe–5Mn–xAl steels was investigated in this study. Four synthetic steels with different Al content were produced in the laboratory. The types of observed inclusions were Al2O3 (pure), Al2O3–MnS, AlN(pure), AlN–MnS, AlON–MnS, AlON and MnS. Increasing Al content from 0.5% to 6% increased the total amount of inclusions by 2.5 times. As the Al content increased from 0.5% to 3%, the number of AlN–MnS inclusions increased significantly. Moreover, the AlN(pure) inclusions appeared in 6% Al containing steel. Thermodynamic calculations confirmed that AlN inclusions formed during cooling of the steel. It is also observed that AlN can precipitate on Al2O3 to form AlN + Al2O3 inclusions, classified as multi-phase AlON inclusions in this study. Furthermore, MnS inclusions could co-precipitate with AlN and Al2O3 inclusions, but it preferred to co-precipitate with AlN inclusions.