ABSTRACT

Atom probe tomography (APT) and selected area electron diffraction (SAED) by transmission electron microscopy (TEM) were applied to nano-scale precipitates formed in a neutron-irradiated iron (99.99% pure) at high temperatures. In the conventional TEM, we discovered donut-type precipitates on the {100} planes that formed at the dilatational side of interstitial type dislocation loops with the Burgers vector of <100> on the habit planes of {100} in the bcc iron lattice. The precipitates were identified as nitride, bct α″-Fe₁₆N₂, by chemical composition and lattice structural analyses using APT and SAED. Image contrasts of the α″-Fe₁₆N₂ in a weak beam dark-field electron microscopy study were carefully analysed with the diffraction vector and the sign of deviation parameter from the Bragg condition, and it was concluded to be a selective visualisation of α″-Fe₁₆N₂ on one of the {100} planes. These results were in agreement with the crystallographic orientation between the α″-Fe₁₆N₂ and matrix iron, thereby bridging a knowledge gap in α″-Fe₁₆N₂ formation during neutron irradiation using a sodium-cooled experimental fast reactor, JOYO, or a 14 MeV D-T neutron source, RTNS-II.

摘要

将原子探针层析成像（APT）和通过透射电子显微镜（TEM）进行的选择区域电子衍射（SAED）应用于高温下在中子辐照铁（纯度为99.99％）中形成的纳米级沉淀物。在常规TEM中，我们发现在{100}平面上形成的甜甜圈型沉淀物是在bcc铁晶格中{100}的惯性平面上的<100>的Burgers向量在间隙类型位错环的膨胀侧形成的。通过化学成分和使用APT和SAED的晶格结构分析，将沉淀物鉴定为氮化物bctα''-Fe ₁₆ N ₂。α″ -Fe ₁₆ N _2的图像对比度在弱束暗场电子显微镜研究中，用衍射矢量和布拉格条件下的偏离参数符号仔细分析，得出结论是{}之一上的α''-Fe ₁₆ N ₂的选择性可视化。100}架飞机。这些结果与α''-Fe ₁₆ N ₂和基体铁之间的晶体取向一致，从而弥合了使用钠冷实验快堆JOYO进行中子辐照过程中α''-Fe ₁₆ N ₂形成过程中的知识缺口。或14 MeV DT中子源RTNS-II。