Study on Micro Segregation of High Alloy Fe-Mn-C-Al Steel

The segregation patterns of solute elements in the Fe-17.1Mn-0.24C-1.38Al steel are systemically investigated by experiments and simulations. The electron probe microanalyzer (EPMA) is conducted to assess possible micro segregation. The result indicates that with the increase of solid fraction in dendrite arms, Mn shows a positive segregation tendency, C uniformly distributes, and Al content slightly fluctuates. Compared with micro segregation models, experimental results of C match well with the Brody-Fleming model. The segregation ratios of Mn are in good agreement with the lever-rule. There is no certain regularity displayed between the experimental and calculation results about the segregation ratios of Al. The matrix of the steel is inhomogeneous with severe Mn and C micro segregation in the inter dendritic zone, whereas Al shows the opposite trend. A multicomponent phase field method coupled to thermodynamic calculations is used to simulate the concentration profiles of solute elements in the dendrite arms, and the numerical results are in favorable agreement with the experimental ones. Finally, the roles of undercooling and cooling rate on dendrite morphology and micro segregation of Mn are investigated. It reveals that large undercoolings could improve Mn segregation, while cooling rates have little effect on the maximum Mn segregation concentration but contribute to reduce the total inter dendritic Mn amount. They both have refinement effects on the dendritic structure. Those are helpful to understand and improve the segregations in Fe-Mn-C-Al steels.