EAPSI: Investigating Grain Boundary Strength of a Helium Implanted Engineering Alloy using Micron-Scale Tensile Testing

根据NPR的一份报告，世界上14%的人？中国的电力是由核能提供的。目前的438座反应堆分布在30个国家，还有15个国家正在建设的67座新核电站，这些反应堆的规格、设计特点和结构材料都有很大的不同。这些结构材料除了在高温高压和腐蚀性降解环境中工作外，还必须承受不断增加的中子辐射损伤。随着反应堆寿命的延长，其安全性和可靠性仍然是最重要的。然而，它们变得难以安全处理和测试，因为它们具有高放射性。已知这种辐射会导致不希望的脆化和突然的过早失效。该项目的重点是通过在反应堆运行温度下将中等能量氦离子束聚焦到样品上来模拟氦生产的高剂量辐射效应。与反应堆中的中子辐照不同，这种技术不会导致样品变得具有放射性，但由于氦的浅穿透深度仅限于微米深度，因此必须在此长度尺度上制造测试样品。将进行微拉伸试验，以研究氦对许多核反应堆中常用的结构材料的晶界强度的影响。这项研究将与澳大利亚核科学与技术组织（ANSTO）的Dhriti Bhattacharyya博士合作进行，他是一位辐射损伤专家，开发了一种新的原位微尺度拉伸测试技术来研究核结构材料。微尺度拉伸试验样品将使用聚焦离子束（FIB）铣削技术由氦注入工程合金制成。这些样本将在扫描电子显微镜（SEM）内进行测试，以有效地拉开材料？的晶界，以测试氦气如何影响其晶界强度，强度决定功能的材料保持完整性和可靠性在延长服务。除了提供定量的机械应力，这种技术允许真实的时间观察局部变形在真实的时间，提供有价值的信息有关的最终故障机制的反应堆组件。选择特定类型的晶界进行研究和不同的微观结构特征可以使用电子背散射衍射（EBSD）和测试后的调查可以使用透射电子显微镜（TEM）和EBSD进行，以进一步了解变形机制和氦的分布，关于它是否沿着材料偏析？的晶界。微拉伸测试方法的发展将在材料研究中有广泛的应用，该奖项是东亚和太平洋夏季研究所计划下的一个奖项，支持美国研究生的夏季研究，由美国国家科学基金会和澳大利亚国家科学基金会共同资助。科学院。

According to a NPR report, 14 percent of the world?s electricity is supplied by nuclear power. The current fleet of 438 reactors spread across 30 nations in addition to the 67 new plants under construction in 15 countries contain a large breadth of specifications, design features, and structural materials. These structural materials must withstand ever increasing amounts of neutron radiation damage in addition to operating in a high temperature and pressure and corrosive degradation environment. Their safety and reliability remain of first importance as reactor lifetimes aspire to be extended. However, they become difficult and expensive to safely handle and test because they become highly radioactive. This radiation has been known to cause unwanted embrittlement and abrupt premature failure. This project focuses on simulating the high dose radiation effect of helium production by focusing a medium energy helium ion beam on a sample at reactor operation temperature. Unlike neutron irradiation in reactors, this technique does not cause the sample to become radioactive, but because the shallow penetration depth of the helium is limited to microns in depth, test samples must be manufactured on this length scale. Micro tensile tests will be performed to investigate the effect of the helium on the grain boundary strength of a structural material commonly used in many nuclear reactors. This research will be conducted in collaboration with Dr. Dhriti Bhattacharyya at the Australian Nuclear Science and Technology Organisation (ANSTO) in Lucas Heights, Australia who is a radiation damage specialist who has developed a novel in-situ micro-scale tensile testing technique to investigate nuclear structural materials. Micro-scale tensile testing specimens will be manufactured out of helium implanted engineering alloys using focused ion beam (FIB) milling techniques. These specimens will be tested inside of a scanning electron microscope (SEM) in a fashion that will effectively pull apart the material?s grain boundaries in order to test how the helium has effected its grain boundary strength, a strength determining feature crucial to the material remaining intact and reliability during extended service. In addition to providing quantitative mechanical stresses, this technique allows for real time observation of local deformation in real time, providing valuable information concerning the ultimate failure mechanism of reactor components. Selecting of specific types of grain boundaries to investigate and different microstructural features can be made using electron backscattered diffraction (EBSD) and post-test investigations can be performed using transmission electron microscopy (TEM) and EBSD to further understand the deformation mechanisms and the distribution of the helium, concerning whether it segregates along the material?s grain boundaries. The methods development of micro-tensile testing will have a wide variety of applications in materials research as a whole, and it will also allow a greater number of labs worldwide to safely conduct research and obtain better statistics with minimal radioactive sample material.This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Australian Academy of Science.