分类： 材料科学 >> 材料科学（综合） 提交时间： 2022-06-20
摘要：
The behavior of nano-voids composed of vacancies (Vs) at grain boundaries (GBs) is fundamental to the design of the radiation tolerance of poly-crystalline metals (PCs) via GB engineering. In this study, based on differential evolution, a framework for determining the stable structure of GB nano-voids is developed. Combining the framework with multiscale simulations, we elucidate the vacancy-accumulation and GB void
formation mechanism under irradiation. A GB-structure dependent picture is revealed. At special coincidence-site-lattice (CSL) GBs of Ʃ5(310) and Ʃ5(210) with a medium V-GB binding energy, the V could be reemitted from the GB and also has driving force to be clustered at the GB, developing particularly stable V-clusters from a linear configuration to a platelet and finally to three-dimensional void that has large strain fields in iron with small bulk modulus and a bulk-void alike structure in the GB with large bulk modulus. A group of vacancies reconstruct their positions during the growth. The ripening is also mediated by the mobility of small V-clusters in addition to free Vs. General high-angle and low-angle GBs trap Vs efficiently, where V-clusters only align one-dimensionally or hardly nucleate. Based on the bonding among the vacancies and their neighboring atoms of a nano-void, we propose a high-accuracy predictive linear energetic model applied to the nano-void both at the iron/molybdenum/tungsten GBs and in the grain interior. The model captures the anisotropic feature of a nano-void and reproduces the oscillated vacancy energy level near a nano-void, showing distinct advantages over conventional continuum model and Wulff construction based energy model. Finally, the collective behavior of multiple GBs plays a role in the GB void formation. The present work offers fundamental mechanistic insights to GB nano-void formation and growth and sets a key step towards GB-void prevention in PCs by reducing the fraction of special CSL-GBs.
分类： 物理学 >> 凝聚态:结构、力学和热性能 提交时间： 2017-08-23
摘要： 软物质物理已成为物理学发展迅速的重要前沿学科。描述软物质复杂非平衡态动力学及其运动规律是理解其宏观性质的关键。内耗与力学谱作为材料缺陷与力学性质研究的重要实验技术，它能够很灵敏探测和研究材料中发生的复杂相变和弛豫动力学过程。文章结合作者近年来的典型工作，介绍了内耗技术在软物质研究中的一些应用，阐述了内耗手段发挥的独特作用。随着内耗测试新方法、新技术和内耗新理论的不断出现和完善，相信未来内耗技术在材料科学和凝聚态物理研究领域将起到越来越重要的作用。
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2017-08-23
摘要： 钨基材料以其高熔点、高导热率、良好的抗中子辐照和抗溅射腐蚀等优异性能，被视为未来核聚变装置中最有前景的面向等离子材料。在聚变服役环境下，14MeV的高能中子以及低能氢/氦粒子流对钨基材料造成严重的辐照损伤。研究材料的辐照损伤与氢氦效应机理对揭示辐照引起材料微观结构与性能的变化以及探索开发新型抗辐照材料具有重要的意义。近年来，随着计算模拟技术的发展，多尺度模拟方法在聚变堆关键材料辐照损伤与氢氦效应机理研究方面有着广泛的应用。本文主要结合作者近几年的研究实践，介绍了纳米晶钨/铁的抗辐照损伤机理、钨中氢滞留机制、合金元素强化界面机制、嬗变元素偏聚及其对氦泡形成机制的影响。通过多尺度模拟方法来获取材料在辐照环境下的不同时间/空间层次的结构演化信息，从而揭示材料的辐照损伤与氢氦效应机理，为聚变堆面向等离子体材料的优化设计与性能调控提供理论基础。
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