Experimental study on the obstacle strength factor to dislocation motion for the evaluation of radiation embrittlement of nuclear materials

为了评估核材料的寿命，研究位错和障碍的相互作用是很重要的。通过透射电镜观察障碍物，从障碍物的大小和数量密度等方面对障碍物引起的诱导硬化进行了评价。这里的重要参数是障碍物强度因子，通常用α表示，目前为止是理论上推导出来的。然而，精度通常是不够的，在许多情况下，习惯上将该参数视为可调参数。另一方面，在某些情况下，障碍物的检测是非常困难的，例如用传统的TEM检测RPVS中的富cu沉淀物。三维原子探针可以检测到这种微小的沉淀物，但由于采样体积的限制，很难获得密度和平均尺寸的统计显著值。在本研究中，这些微小的析出物在与析出物相互作用的定位线上被检测到为尖点。这是这里发展的技术的主要成就之一。此外，障碍物强度参数α可以直接从尖顶角测量。宏观力学试验结果与原位透射电镜观察结果一致。结果表明了该方法的有效性。对位错与障碍物的相互作用过程进行了MD模拟。这些结果被用来了解无法通过原位透射电镜研究的微观过程。MD研究进一步验证了本研究的方法。超声衰减测量在外部应力和振幅依赖的内摩擦测量也进行了。前一种技术是为了评价非破坏性辐射硬化而发展起来的。原位透射电镜研究、超声衰减和内摩擦都结合起来，对位错和障碍物的相互作用有了全面的认识。本研究证明了外应力下的超声衰减测量是一种很有前途的辐射硬化无损评价方法。少

For the evaluation of lifetime of nuclear materials, it is important to examine the interaction of dislocations and obstacles. A number of researches have been devoted for this objective by observing obstacles by TEM, and from their size and number density, the induced hardening due to these obstacles was evaluated. Here, the important parameter is the obstacle strength factor that usually denoted as α, and was derived theoretically so far. However, the accuracy was usually not sufficient, and it was a customary in many cases that this parameter was treated as an adjustable parameter. The detection of obstacles, on the other hand, is very difficult in some cases, e.g. Cu-rich precipitates in RPVS with conventional TEM. Three-D Atom Probe can detect such tiny precipitates, but because of the limited size of sampling volume, it is difficult to obtain statistically significant value of the density and average size. In the present study, these tiny precipitates were detected as cusps on di … More slocation lines interacting with the precipitates. This is one of the major accomplishments of the technique developed here. Moreover, the obstacle strength parameter α can be measured directly from the apex angle of the cusp. Striking agreement was obtained between the hardening obtained from macroscopic mechanical test with that obtained from in situ TEM. This result shows the validity of the technique. MD simulation of the interaction process between dislocations and obstacles was carried out. The results were used to understand the microscopic process that cannot be examined by in situ TEM study. MD study further verified the method developed in this study.Ultrasonic attenuation measurements under external stress and amplitude dependent internal friction measurements were also carried out. The former technique was developed in order to evaluate non-destructively radiation hardening. In situ TEM study, ultrasonic attenuation, and internal friction are all combined to yield a comprehensive view on the interaction of dislocations and obstacles. In the present study, it was demonstrated that ultrasonic attenuation measurement under external stress is a very promising method for non-destructive evaluation of radiation hardening. Less