Chemical variation occurring during the solidification process can cause undesirable effects on the material property, especially for alloys with high solute content. The current study investigated the distributions of solute elements in directional solidified Fe–Mn–C–Al TWIP steels and compared the micro-segregation with various pulling rates and C contents using the phase field model and the grid analysis based on the data performed by EPMA, which could provide advice for mitigating micro-segregation in high Mn steel. The results indicated that C and Mn preferentially segregated toward the liquid phase, while Al entered the solid phase. The occurrence of solid-state diffusion was observed, which led to a homogenization effect in the solid phase during solidification. The pulling speed increase made a more severe micro-segregation because the change of pulling speeds had more effect on the SDAS than on the local solidification time; thus, the dimensionless diffusion time decreased with increasing pulling rates, representing a more serious micro-segregation. For a C content increasing from 0.06 to 0.68 wt pct, the micro-segregation level of C and Al reduced first and then increased, which was caused by the change in the solidification mode. The continuous accumulation of solute elements and the slower solute element diffusion in austenite in combination led to the presence of more severe micro-segregation in the case of one-phase solidification. Besides, a C content increase could attract Mn, resulting in more serious Mn micro-segregation.

中文翻译：

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定向凝固 Fe-Mn-C-Al TWIP 钢的微观偏析研究

凝固过程中发生的化学变化会对材料性能产生不良影响，特别是对于溶质含量高的合金。目前的研究调查了定向凝固 Fe-Mn-C-Al TWIP 钢中溶质元素的分布，并使用相场模型和基于 EPMA 数据的网格分析比较了不同提拉速率和 C 含量下的微观偏析，这可以为减轻高锰钢中的微观偏析提供建议。结果表明，C和Mn优先向液相偏析，而Al进入固相。观察到固态扩散的发生，这导致了凝固过程中固相的均化效应。提拉速度的增加导致更严重的微观偏析，因为提拉速度的变化对SDAS的影响大于对局部凝固时间的影响；因此，无量纲扩散时间随着提拉速率的增加而减少，代表更严重的微观偏析。当C含量从0.06增加到0.68wt%时，C和Al的微观偏析水平先降低后升高，这是由凝固模式的变化引起的。溶质元素的不断积累和较慢的溶质元素在奥氏体中的扩散相结合，导致在一相凝固的情况下存在更严重的微观偏析。此外，C含量的增加会吸引Mn，导致更严重的Mn微观偏析。