Mechanics and Kinetics of Void Swelling in Irradiated Nanoporous Materials

下一代核反应堆对能够经受高温和高剂量辐射的先进材料的发现有着巨大的需求。在这些工作条件下，大量的金属材料会产生空洞，导致脆化和随后的失效。当辐射诱导原子缺陷迁移到其他地方时，空洞膨胀就会发生，留下一簇簇的空位。这些空位团簇形成空位并不断长大。然而，主要研究人员的初步研究显示了相反的现象：即在辐射过程中，具有纳米级气孔的金属中的空洞缩小而不是扩大。这项研究将调查这一现象，并可能从根本上增加对辐射损害缓解的基本机制的理解。一个积极的结果将加强先进核能系统中耐辐射纳米孔材料的设计。在这个项目中，将特别努力招收女性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主要国家实验室的夏季研究经验。这个项目的目标是通过模拟和实验相结合的方法，了解在纳米多孔金属材料中故意引入纳米空洞可以吸收和消除辐射诱导的点缺陷，最终显著减少空洞膨胀和减轻辐射脆化的基本机制。这里提出的创新概念是利用纳米空洞及其应力场来捕获、存储和湮灭与辐射损伤相关的各种缺陷物种，并恢复持续吸收缺陷的能力。此外，与块体全密度金属中经常观察到的辐射脆化相比，纳米多孔金属可能具有增强的可塑性。本研究将原位辐射实验与相场模拟相结合来研究孔洞膨胀的动力学，并结合原位纳米力学测试与位错动力学模型来探索辐照纳米多孔金属的力学与塑性。

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.