The role of Mg–Si–Al nitrides in the nucleation of low-sulfur spheroidal graphite Fe–C–Si alloys has been previously documented. It was demonstrated that when acting as nuclei, in most cases, these nitrides are not singular crystals but are part of complex inclusions. To further document the complexities of this phenomenon a Fe–C–Si melt with 3.55%C and 3.1%Si was treated with a 2.5Ca1.6Zr1.4Al inoculating alloy and poured into a thermal analysis (TA) cup. Samples extracted from the TA cup were analyzed through quantitative optical microscopy. Then, Field Emission Gun Scanning Electron Microscopy was used to identify the nature of the non-metallic inclusions serving as nuclei. It was demonstrated that the main nucleation sites are Mg–Si–Al nitrides that many times nucleate on sulfides. Also, some Ti carbo-nitrides were observed growing on the corners of these nitrides. Further, Selected Area Electron Diffraction techniques provided information on the crystallinity of the nucleus, as well as on the graphite/nucleus interface and on graphite growth in the immediate vicinity of the nitride. Transmission Kikuchi Diffraction patterns suggest that the nitrides are MgSiN₂ polycrystals with orthorhombic lattice. Turbostratic graphite was identified in the proximity of the nucleus. It supports a better understanding of the growth of graphite on the nucleating phase and brings some clarity to the ongoing debate on the mechanisms of graphite growth.

Mg-Si-Al 氮化物在低硫球状石墨 Fe-C-Si 合金的形核中的作用之前已有文献记载。结果表明，当作为晶核时，在大多数情况下，这些氮化物不是单晶，而是复杂夹杂物的一部分。为了进一步证明这种现象的复杂性，用 2.5Ca1.6Zr1.4Al 孕育合金处理含有 3.55%C 和 3.1%Si 的 Fe-C-Si 熔体并倒入热分析 (TA) 杯中。通过定量光学显微镜分析从 TA 杯中提取的样品。然后，使用场发射枪扫描电子显微镜来识别作为核的非金属夹杂物的性质。结果表明，主要的成核位点是 Mg-Si-Al 氮化物，它多次在硫化物上成核。还，在这些氮化物的角上观察到一些 Ti 碳氮化物生长。此外，选区电子衍射技术提供了关于核结晶度、石墨/核界面和氮化物附近石墨生长的信息。透射菊池衍射图案表明氮化物是 MgSiN₂具有正交晶格的多晶。在原子核附近发现了涡轮层状石墨。它支持更好地理解石墨在成核阶段的生长，并为正在进行的关于石墨生长机制的辩论带来一些清晰。