The potential of different inclusions to act as heterogeneous nucleation sites for primary austenite during solidification of a lightweight Fe–30Mn–5.5Al–1.5C–1.2Si steel was analyzed by thermodynamic calculations and experimental heats. Thermodynamic simulations and lattice disregistry calculations were utilized to predict the stability and nucleation potential of different inclusions. TiN was considered as the grain-refining addition because of the success of this inoculant in other austenitic steel castings. Addition of TiN was performed through the use of a pre-made master alloy containing a large volume fraction of fine TiN inclusions. Experimental castings were produced from cylindrical phenolic resin-bonded sand molds with a bottom chill to introduce directional solidification. Additions of 0.5 and 1.5% of the TiN containing master alloy, up to 0.29 wt% Ti addition to the melt, did not yield detectable grain refinement of the as-cast grain structure when compared to the steel castings without additions. Scanning electron microscopy revealed that the inclusions present in the resulting castings consisted mainly of Ti(C,N) with up to a 0.4% area fraction, and this suggests that the original TiN inclusions were at least partially dissolved. Thermodynamic modeling predicted the equilibrium stability of Ti₄C₂S₂ at temperatures above 1440 °C. Although this phase was not observed experimentally, a nanoscale interface layer of Ti₄C₂S₂ or sulfur adsorption on the surface of the Ti(C,N) inclusions may be responsible for poisoning of the nuclei.

中文翻译：

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TiN的添加对轻质Fe-Mn-Al钢组织的影响

通过热力学计算和实验热分析了轻质Fe-30Mn-5.5Al-1.5C-1.2Si钢凝固过程中不同夹杂物作为一次奥氏体异质形核位点的潜力。利用热力学模拟和晶格脱离计算来预测不同夹杂物的稳定性和成核潜能。TiN被认为是晶粒细化的添加剂，因为这种孕育剂在其他奥氏体钢铸件中很成功。TiN的添加是通过使用预制的中间合金来完成的，该中间合金包含大量的TiN细小夹杂物。实验铸件由圆柱形酚醛树脂粘结砂模制成，底部冷却以引入定向凝固。添加0.5％和1.5％的含TiN中间合金，与不添加钢铸件相比，向熔体中添加多达0.29 wt％的Ti时，铸态晶粒组织无法产生可检测的晶粒细化。扫描电子显微镜显示，所得铸件中存在的夹杂物主要由Ti（C，N）组成，面积分数最高为0.4％，这表明原始的TiN夹杂物至少部分溶解。热力学模型预测钛的平衡稳定性 这表明原始的TiN夹杂物至少部分溶解了。热力学模型预测钛的平衡稳定性 这表明原始的TiN夹杂物至少部分溶解了。热力学模型预测钛的平衡稳定性温度高于1440°C时为₄ C ₂ S ₂。尽管从实验上未观察到该相，但Ti ₄ C ₂ S ₂的纳米级界面层或Ti（C，N）夹杂物表面上的硫吸附可能是原子核中毒的原因。