The stacking fault tetrahedron (SFT) formation displays a pronounced size effect, progressing from vacancy equilateral triangular plate to perfect SFT, and eventually to truncated SFT, as demonstrated in numerous irradiated face-centered cubic metals. However, the presence of distinct SFT structures in F321 stainless steel has not been reported. This study explored the SFT formation mechanism in irradiated F321 stainless steel using transmission electron microscopy (TEM), molecular dynamics (MD) simulations, and machine learning. SFTs, Frank loops, and Lomer-Cottrell locks were found to be widely generated in the irradiated F321 steel. The critical size for truncated and perfect SFTs was determined using MD simulations; the results were consistent with the theoretical predictions. Additionally, the twin boundaries observed through TEM, which were attributed to the elevated tensile stress near the boundaries, facilitated the formation of perfect SFTs. Moreover, interstitial Frank loops also facilitated the formation of perfect SFTs. This study also explored the influence of variations in Ni and Cr concentrations on the critical size n1 for the transition from vacancy plates to perfect SFTs and n2 for the transition from perfect SFTs to truncated SFTs, using a combination of MD and machine learning methods. As the Ni concentration increased and the Cr concentration decreased, n1 and n2 increased; conversely, the critical sizes decreased when the Ni concentration decreased and the Cr concentration increased. These insights reveal the systematic mechanism of SFT formation under varied conditions, offering new perspectives for understanding the nano-defects in F321 stainless steel.

中文翻译：

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了解 FCC 不锈钢中的堆叠断层四面体形成：透射电子显微镜、分子动力学和机器学习的融合


堆积断层四面体 （SFT） 的形成显示出明显的尺寸效应，从空位等边三角板发展到完美的 SFT，最后到截短的 SFT，如许多辐照面心立方金属所示。然而，F321 不锈钢中存在不同的 SFT 结构尚未见报道。本研究使用透射电子显微镜 （TEM） 、分子动力学 （MD） 模拟和机器学习探讨了辐照 F321 不锈钢中 SFT 的形成机制。发现 SFT、Frank 环和 Lomer-Cottrell 锁在辐照 F321 钢中广泛产生。使用 MD 模拟确定截断和完美 SFT 的临界大小;结果与理论预测一致。此外，通过 TEM 观察到的孪晶界（归因于晶界附近较高的拉伸应力）促进了完美 SFT 的形成。此外，间隙 Frank 循环也促进了完美 SFT 的形成。本研究还结合使用 MD 和机器学习方法，探讨了 Ni 和 Cr 浓度的变化对从空位板过渡到完美 SFT 的临界尺寸 n1 和从完美 SFT 过渡到截短 SFT 的临界尺寸 n2 的影响。随着 Ni 浓度的增加和 Cr 浓度的降低，n1 和 n2 增加;相反，当 Ni 浓度降低而 Cr 浓度增加时，临界尺寸减小。这些见解揭示了不同条件下 SFT 形成的系统机制，为理解 F321 不锈钢中的纳米缺陷提供了新的视角。