Effect of Al and N Contents on the Characteristics of Non-metallic Inclusions and Precipitation Behaviors in Unidirectionally Solidified Fe-Mn-C-Al TWIP Alloys

Non-metallic inclusions have an important influence on the performance of steel. Especially, the precipitation control of inclusions is particularly significant during the solidification process in high Mn and Al TWIP steel. Regulatory alloy components as one of the effective methods, it was investigated that the effect of Al and N contents on the characteristics of non-metallic inclusions and its precipitation behaviors in unidirectionally solidified Fe-Mn-C-Al TWIP alloys. The results showed that the increase of initial Al and N concentration promoted their segregation each other, and the AlN particle size was also increased. Thermodynamic analysis of the precipitation of AlN and AlON revealed that the effect of N content on the precipitation of AlN was greater than that of Al content which showed the critical fs to initiate inclusion precipitation decrease. On the contrary, the effect of Al content on the precipitation of AlON was greater. Under the condition where the oxygen content was basically similar, the increase of Al content made the primary bonding with O atoms reducing aO in the melt, and the change of N content became the main factor influencing AlN precipitation.