The solidification path and the σ-phase precipitation mechanism in the S31254 (UNS designation) steel are investigated thanks to Quenching during Directional Solidification (QDS) experiments accompanied by scanning electron microscopy observations and electron backscattered diffraction (EBSD) analysis. Considering experimental conditions, the γ-austenite is found to be the primary solidifying phase (1430 °C), followed by δ-ferrite (1400 °C, ≈ 87 pct solid fraction). The σ-phase appears in the solid-state through the eutectoid decomposition of the δ-ferrite: δ → σ + γ₂ (1210 °C), whereas the σ-phase is predicted to form from the austenite at 1096 °C in equilibrium conditions. The resulting temperatures of solidification path and phase transformation are compared with Gulliver–Scheil model and equilibrium calculations predicted using Thermo-Calc^© software. It is shown that the thermodynamics calculations agree with experimental results of solidification path. The EBSD analysis show that the δ-ferrite has δNW2 ORs with the σ-phase.

通过定向凝固（QDS）实验中的淬火，扫描电子显微镜观察和电子背散射衍射（EBSD）分析，研究了S31254（UNS名称）钢中的凝固路径和σ相析出机理。考虑到实验条件，发现γ-奥氏体是主要的凝固相（1430°C），其次是δ-铁素体（1400°C，≈87 pct固相率）。所述σ -PHASE通过的共析分解出现在固态δ δ-铁素体：δ →交通σ + γ ₂（1210℃），而σ在平衡条件下，预计在1096​​°C时奥氏体会形成相。将所得的凝固路径和相变温度与Gulliver-Scheil模型进行比较，并使用Thermo-Calc ^©软件预测平衡计算。结果表明，热力学计算结果与凝固路径的实验结果吻合。该EBSD分析表明，δ δ-铁素体具有δ NW2手术室与σ -PHASE。