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，研究位错和障碍物的相互作用是很重要的。为此，人们利用透射电子显微镜观察障碍物进行了大量的研究，并从障碍物的大小和数密度两个方面对障碍物引起的诱导硬化进行了评价。这里，重要的参数是障碍物强度因子，通常表示为α，到目前为止都是从理论上推导出来的。然而，精度通常是不够的，在许多情况下，这一参数被视为可调参数是一种惯例。另一方面，在某些情况下，检测障碍物是非常困难的，例如用常规的透射电子显微镜检测RPV中的富铜沉淀物。三维原子探头可以探测到如此微小的沉淀物，但由于采样体积的限制，很难获得具有统计学意义的密度和平均尺寸。在本研究中，这些微小的沉淀物被检测为di…上的尖端。更多的位置线与沉淀物相互作用。这是这里开发的技术的主要成就之一。此外，障碍物强度参数α可以从尖端的角度直接测量。宏观力学试验所得的硬化与原位透射电子显微镜所得的硬化结果有显著的一致性。这一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分子动力学模拟。这些结果被用来理解不能用原位透射电子显微镜研究的微观过程。MD研究进一步验证了本文提出的方法，并进行了外应力下的超声衰减测量和内耗随振幅变化的测量。前者是为了评估非破坏性辐射加固而发展起来的。原位透射电子显微镜研究、超声波衰减和内耗结合在一起，对位错和障碍物的相互作用产生了全面的看法。在本研究中，外应力下的超声衰减测量是一种非常有前途的辐射加固无损评价方法。较少

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