Mechanics and Kinetics of Void Swelling in Irradiated Nanoporous Materials

人们迫切需要发现能够经受高温和高剂量辐射的先进材料，用于下一代核反应堆。在这些操作条件下，大量的金属材料产生空隙，导致脆化和随之而来的失效。当辐射诱导原子缺陷迁移到别处时，空隙膨胀发生，留下空位簇。这些空位团形成空洞并不断生长。然而，主要研究人员的初步研究显示了相反的现象：即具有纳米级孔隙的金属中的空隙在辐射期间收缩而不是膨胀。这项研究将调查这一现象，并可能从根本上增加对辐射损伤减轻的基本机制的理解。一个积极的结果将提高先进核能系统的耐辐射纳米多孔材料的设计。在这个项目中，将特别努力招收女生和其他少数民族学生。此外，与阿贡国家实验室和洛斯阿拉莫斯国家实验室的科学家合作，将为研究生提供一流国家实验室的夏季研究经验。该项目的目标是通过建模和实验相结合，了解在纳米多孔金属材料中故意引入纳米空隙的基本机制，通过该机制可以吸收和消除辐射诱导的点缺陷，并最终显著减少空隙膨胀并减轻辐射脆化。这里提出的创新概念是利用纳米空隙及其应力场来捕获、存储和消除与辐射损伤相关的各种缺陷物种，并恢复连续吸收缺陷的能力。此外，纳米多孔金属可能具有增强的塑性相比，经常观察到的辐射脆化的散装全致密的对应物。本研究将原位辐射实验与相场模拟相结合，探讨孔洞膨胀的动力学，并将原位纳米力学测试与位错动力学模拟联合收割机相结合，探讨辐照纳米多孔金属的力学和塑性。

There is a significant demand for the discovery of advanced materials that can survive high temperature and high-dose radiations for next generation nuclear reactors. Under these operating conditions, a large number of metallic materials develop voids that result in embrittlement and consequent failure. Void swelling occurs as radiation induces atomic defects that migrate elsewhere leaving clusters of vacant positions behind. These vacancy clusters form voids and grow continuously. The principal investigators' initial study shows just the opposite phenomenon, however: that is, voids in metals with existing nanoscale pores shrink rather than expand during radiation. This research will investigate this phenomenon and may add radically to the understanding of fundamental mechanisms of radiation damage mitigation. A positive outcome will enhance the design of radiation tolerant nanoporous materials for advanced nuclear energy systems. In this project, special effort will be made to recruit female and other minority students. Additionally, collaborations with scientists at Argonne National Laboratories and Los Alamos National Laboratory will offer graduate students summer research experience at premier national labs. The goal of this project is to understand, via a combination of modeling and experiments, the fundamental mechanisms through which deliberately introduced nanovoids in nanoporous metallic materials can absorb and eliminate radiation induced point defects, and ultimately curtail void swelling significantly and alleviate radiation embrittlement. The innovative concepts put forward here are the possibility of utilizing nanovoids and their stress field to trap, store and annihilate various defect species associated with radiation damage, and restore the capability to absorb defects continuously. Furthermore, nanoporous metals may have enhanced plasticity in comparison to radiation embrittlement frequently observed in bulk fully-dense counterparts. This study integrates in situ radiation experiments with phase field modeling to investigate the kinetics of void swelling, and combine in situ nanomechanical testing with dislocation dynamics modeling to explore mechanics and plasticity of irradiated nanoporous metals.