The influence of Ce addition on the solidification structure and σ phase of super austenitic stainless steel S32654 was systematically investigated via microstructural characterization and thermodynamic calculation. The results indicate that a small addition of Ce could modify MgO and MnS into Ce-bearing inclusions Ce₂O₃ and Ce₂O₂S. Ce addition led to noticeable refinement of both the dendrite structure and σ phase. The refinement mechanism could be attributed to the combined actions of effective Ce-bearing inclusions and solute Ce. Effective Ce-bearing inclusions could serve as heterogeneous nucleation cores of austenite as well as σ phase, which provided a favorable prerequisite for their refinement. Solute Ce significantly enhanced the undercooling degree of the system, further promoting dendrite structure refinement. Meanwhile, solute Ce improved the eutectic precipitation conditions of σ phase and further promoted its nucleation, while the dendrite refinement limited its growth space. Finally, more fine and dispersed σ phase particles formed in S32654 with Ce addition. The refinement of dendrite structure and σ phase will reduce the temperature and time required for high-temperature homogenization, which is beneficial to the hot working of this steel.

通过显微组织表征和热力学计算，系统研究了Ce添加对超级奥氏体不锈钢S32654凝固组织和σ相的影响。结果表明，少量的Ce可以将MgO和MnS改性成含Ce的夹杂物Ce ₂ O ₃和Ce ₂ O ₂S. Ce 的添加导致枝晶结构和 σ 相的显着细化。细化机制可归因于有效的含 Ce 夹杂物和溶质 Ce 的共同作用。有效的含Ce夹杂物既可以作为奥氏体的异质形核核心，也可以作为σ相，为其细化提供了有利的先决条件。溶质Ce显着增强了体系的过冷度，进一步促进了枝晶结构的细化。同时，溶质Ce改善了σ相的共晶析出条件，进一步促进了其形核，而枝晶细化限制了其生长空间。最后，随着 Ce 的加入，在 S32654 中形成了更细和分散的 σ 相颗粒。