With the emerging significance of creating an acicular ferrite microstructure to provide an optimum set of properties in steel, MnS precipitation behavior on a MnO–SiO₂ inclusion at the solid-liquid coexistence temperature was experimentally investigated and thermodynamically elucidated in this study. Using a direct method of forming inclusions, alloy samples with varying sulfur concentrations [Fe-1.1Mn-0.10Si-0.05O-S (initial mass%); 0.005 to 0.031 initial mass% S] were prepared by holding at the solid-liquid coexistence temperature for 1 hour.

In samples with less than 0.011 mass% sulfur, the formation of a MnO–SiO₂ inclusion with a SiO₂-rich precipitate was observed. Formation of SiO₂ was described as a consequence of silicon enrichment in the liquid phase, which, under appropriate thermodynamic conditions, homogeneously precipitated and later on coalesced with the primary MnO–SiO₂ phase. On the other hand, in samples with more than 0.022 mass% sulfur, heterogeneous precipitation of MnS along the boundary of the primary MnO–SiO₂ inclusion and the alloy matrix was observed. Also, the SiO₂-rich phase was found to disappear with increasing sulfur addition. Since the likelihood of heterogeneous nucleation is higher than homogeneous nucleation, it was assumed that MnS precipitation on the surface of the primary MnO–SiO₂ prevented the secondary SiO₂-rich inclusion from coalescing with the existing MnO–SiO₂ inclusion. This was also further validated for solute enrichment in the liquid phase, wherein MnS precipitation temperature was found to shift to higher temperatures in alloys with higher sulfur content.

随着创建针状铁素体显微组织以提供钢的最佳性能的新兴重要性，本实验研究并在热力学上阐明了在固液共存温度下MnS-SiO ₂夹杂物中MnS的析出行为。使用直接形成夹杂物的方法，可以检测出硫含量不同的合金样品[Fe-1.1Mn-0.10Si-0.05OS（初始质量％）；通过在固液共存温度下保持1小时来制备0.005〜0.031质量％的初始S。

在硫含量少于0.011质量％的样品中，观察到形成了MnO-SiO ₂夹杂物和富含SiO _2的沉淀物。SiO _2的形成被描述为液相中硅富集的结果，在适当的热力学条件下，硅富集了均匀的沉淀，随后与MnO-SiO ₂初生相合并。另一方面，在硫含量大于0.022质量％的样品中，观察到沿主要MnO-SiO ₂夹杂物和合金基体边界的MnS异相沉淀。另外，SiO ₂发现富硫相随着硫添加的增加而消失。由于异相成核的可能性比均相成核更高，它被假设主的MnO-的SiO的表面上的MnS沉淀₂防止二次的SiO ₂从与现有的MnO-的SiO富含聚结列入₂夹杂物。液相中的溶质富集也得到了进一步验证，其中发现MnS沉淀温度在硫含量较高的合金中会转变为较高的温度。