Microsegregation in low carbon Fe-Mn-Si-Al TWIP steel

Microsegregation in low carbon Fe-25Mn-3Si-3Al TWIP steel produced in the laboratory and steel plant were systematically investigated by electron microprobe analysis. The results show that the dendritic segregation is serious in both the laboratorial ingot and mold casting after AOD steelmaking at the industrial plant. Additionally,microsegregation in the AOD ingot is higher,and the greatest amounts of segregation of Mn and Al are measured to be 6.8% and 2.4%,respectively. After electroslag remelting in the steel plant,the grain boundary segregation is serious,and it completely improves after a forging process. A higher alloy composition and a wider crystallization temperature interval are the main reasons for the serious microsegregation. All specimens of the TWIP steel have the same law. Mn shows obvious negative segregation,Al and Si exhibit positive segregation,and Al has the highest degree of segregation. The elements' solute distribution coefficient K of the TWIP steel was calculated using the Thermo-Calc software. It is found that the microsegregation laws of Mn and Al in theory are opposite to those in the experiment,and the main reason is silicon content.