FeCrAl alloys are candidate materials for manufacturing accident-tolerant fuel (ATF) cladding intended for light water reactors to increase fuel reliability and safety during design-basis and beyond-design-basis accident scenarios. The evolution of the materials' surface characteristics, microstructure, and mechanical properties when exposed to the Critical Heat Flux (CHF) in flow boiling testing is crucial for safety analysis while providing insights into their thermal-hydraulic performance in nuclear reactors. After CHF, the surface chemistry of two FeCrAl alloys, APMT and C26M, was studied to understand their evolution at the early stage of high-temperature excursions in short time periods. The results indicated a thin layer composed of oxides and hydroxides of Al, Cr, and Fe with varying proportions at different depths in the layer, as indicated by X-ray photoelectron spectroscopy (XPS) and depth profiling. The cross-sections prepared by focused ion beam (FIB) revealed the growth of an oxide layer, in the range of 90-180 nm thick, on the alloys' surfaces. The evolution of the materials' surface chemistry also led to a noticeable post CHF excursion increase in their wettability, with a slight increase in roughness. The investigation of the materials' mechanical properties indicated a modest increase in hardness by 10-15% as well as an increase in their yield strength, as evidenced by the microindentation and ring compression tests conducted before and after CHF testing. Scanning electron Microscopy (SEM) and X-ray diffraction (XRD) were used to investigate microstructural features of the materials and their changes after CHF treatment.

FeCrAl 合金是制造用于轻水反应堆的容灾燃料 (ATF) 包壳的候选材料，可在设计基准和超出设计基准的事故场景中提高燃料的可靠性和安全性。在流动沸腾测试中暴露于临界热通量 (CHF) 时，材料的表面特性、微观结构和机械性能的演变对于安全分析至关重要，同时提供对其在核反应堆中的热工水力性能的深入了解。在 CHF 之后，研究了两种 FeCrAl 合金 APMT 和 C26M 的表面化学，以了解它们在短时间内高温偏移的早期阶段的演变。结果表明，薄层由 Al、Cr 和 Fe 的氧化物和氢氧化物组成，在该层的不同深度处具有不同的比例，如 X 射线光电子能谱 (XPS) 和深度剖析所示。通过聚焦离子束 (FIB) 制备的横截面显示，在合金表面上生长了 90-180 nm 厚的氧化层。材料表面化学的演变也导致其润湿性在 CHF 偏移后显着增加，粗糙度略有增加。CHF 测试前后进行的显微压痕和环压缩测试证明，对材料机械性能的调查表明，硬度适度增加了 10-15%，并增加了屈服强度。扫描电子显微镜（SEM）和X射线衍射（XRD）用于研究材料的微观结构特征及其CHF处理后的变化。