Abstract FeCrAl alloys are regarded as excellent potential candidates of fuel claddings in nuclear reactors. To further understand the evolution of helium bubbles and dislocation loops during the annealing process, He+-irradiated TEM samples with a normal chemical composition of Fe-13.2Cr-5.6Al-2Mo-2ZrC (wt.%) were annealed and observed by in-situ transmission electron microscopy. The dislocation density decreased with the increase of annealing temperature, but the loop size was opposite. No obvious bubbles were observed at the annealing temperature below 772 K, even if the annealing time was prolonged. The average diameters of helium bubbles in the sample annealed at 772, 872 and 972 K for 60 min were 1.4, 2.1 and 3.1 nm, respectively, which indicated that bubble sizes increased with the rise of annealing temperature. When the temperature was increased to 1072 K, the bubbles grew rapidly while their density decreased significantly. The dynamic process, during which two or more bubbles merged into one large-sized bubble, was observed. The migration and coalescence of small bubbles should be attributed to the control of surface diffusion mechanism.

中文翻译：

---

退火过程中预氦辐照的 FeCrAl 合金中位错环和氦气泡演变的原位 TEM 观察

摘要 FeCrAl合金被认为是核反应堆燃料包壳的优良潜在候选材料。为了进一步了解退火过程中氦气泡和位错环的演变，对具有正常化学成分 Fe-13.2Cr-5.6Al-2Mo-2ZrC (wt.%) 的 He+辐照 TEM 样品进行退火并通过 in-原位透射电子显微镜。位错密度随着退火温度的升高而降低，但环尺寸相反。即使延长退火时间，在低于 772 K 的退火温度下也没有观察到明显的气泡。在 772、872 和 972 K 下退火 60 min 的样品中氦气泡的平均直径分别为 1.4、2.1 和 3.1 nm，这表明气泡尺寸随着退火温度的升高而增大。当温度升高到 1072 K 时，气泡迅速增长，而其密度显着下降。观察到两个或多个气泡合并成一个大气泡的动态过程。小气泡的迁移和聚结应归因于表面扩散机制的控制。