Zhang Yanwen, Osetsky Yuri N, Weber William J
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States.
Chem Rev. 2022 Jan 12;122(1):789-829. doi: 10.1021/acs.chemrev.1c00387. Epub 2021 Oct 25.
The development of advanced structural alloys with performance meeting the requirements of extreme environments in nuclear reactors has been long pursued. In the long history of alloy development, the search for metallic alloys with improved radiation tolerance or increased structural strength has relied on either incorporating alloying elements at low concentrations to synthesize so-called dilute alloys or incorporating nanoscale features to mitigate defects. In contrast to traditional approaches, recent success in synthesizing multicomponent concentrated solid-solution alloys (CSAs), including medium-entropy and high-entropy alloys, has vastly expanded the compositional space for new alloy discovery. Their wide variety of elemental diversity enables tunable chemical disorder and sets CSAs apart from traditional dilute alloys. The tunable electronic structure critically lowers the effectiveness of energy dissipation via the electronic subsystem. The tunable chemical complexity also modifies the scattering mechanisms in the atomic subsystem that control energy transport through phonons. The level of chemical disorder depends substantively on the specific alloying elements, rather than the number of alloying elements, as the disorder does not monotonically increase with a higher number of alloying elements. To go beyond our knowledge based on conventional alloys and take advantage of property enhancement by tuning chemical disorder, this review highlights synergistic effects involving valence electrons and atomic-level and nanoscale inhomogeneity in CSAs composed of multiple transition metals. Understanding of the energy dissipation pathways, deformation tolerance, and structural stability of CSAs can proceed by exploiting the equilibrium and non-equilibrium defect processes at the electronic and atomic levels, with or without microstructural inhomogeneities at multiple length scales. Knowledge of tunable chemical disorder in CSAs may advance the understanding of the substantial modifications in element-specific alloy properties that effectively mitigate radiation damage and control a material's response in extreme environments, as well as overcome strength-ductility trade-offs and provide overarching design strategies for structural alloys.
长期以来，人们一直在追求开发性能满足核反应堆极端环境要求的先进结构合金。在合金发展的漫长历史中，寻找具有更高辐射耐受性或更高结构强度的金属合金，要么依靠低浓度添加合金元素来合成所谓的稀合金，要么引入纳米尺度特征来减轻缺陷。与传统方法不同，最近在合成多组分浓固溶体合金（CSA）方面取得的成功，包括中熵合金和高熵合金，极大地扩展了新合金发现的成分空间。它们丰富的元素多样性使得化学无序可调，这使CSA有别于传统的稀合金。可调的电子结构显著降低了通过电子子系统进行能量耗散的效率。可调的化学复杂性还改变了原子子系统中的散射机制，而原子子系统控制着通过声子的能量传输。化学无序程度在很大程度上取决于特定的合金元素，而不是合金元素的数量，因为无序不会随着合金元素数量的增加而单调增加。为了超越我们基于传统合金的知识，并通过调节化学无序来利用性能增强，本综述强调了由多种过渡金属组成的CSA中涉及价电子以及原子级和纳米级不均匀性的协同效应。通过利用电子和原子水平上的平衡和非平衡缺陷过程，无论是否存在多尺度的微观结构不均匀性，都可以深入了解CSA的能量耗散途径、变形耐受性和结构稳定性。了解CSA中可调的化学无序，可能会加深对特定元素合金性能的实质性改变的理解，这些改变有效地减轻了辐射损伤，并控制了材料在极端环境中的响应，同时克服强度-延展性权衡，并为结构合金提供总体设计策略。
