DMREF: Collaborative Research: Fundamentals of Short-Range Order-Assisted Alloy Design: Thermodynamics, Kinetics, Mechanics

众所周知，纳米尺度上原子的排列顺序决定着材料的性质和性能，但对于许多结构合金来说，对性质、性能和结构之间的定量关系，特别是对原子的短程排列顺序，还缺乏了解。了解这些关系有可能使新的高强度、耐腐蚀材料用于交通、能源和基础设施应用。该设计材料变革和工程我们的未来（DMREF）奖支持研究，以发展对短程订购的基本理解，以确定具有优越性能的新金属材料的设计指南。短程序合金在短程内具有硬而脆的金属间化合物的特点，但在中长期内也具有软的纯金属或固溶体的特点。尽管传统的理解表明并非如此，但越来越多的证据表明，短程排序可以导致机械性能的意想不到的改善。将探索一种短程有序辅助合金设计理念，作为克服物理冶金中基本强度-韧性限制的新途径。本研究的总体目标是建立基本的认识和通用的设计规则，使其能够有效地利用近程顺序来实现极端环境下的抗损伤。这项研究的概念被纳入当地科学博物馆的教育模块中，通过学生研究人员的积极参与，这项工作将产生进一步的教育效益。这项工作旨在揭示控制短程有序稳定性和特性的因素，了解短程有序辅助变形微/纳米力学的基本原理，并设计出克服当前强度和韧性限制的新型复杂浓缩合金。有必要了解如何控制短程有序化学，尺寸和强度的特定方面，以及这些变化如何影响与位错的相互作用。为此，最重要的挑战之一是关于特征。近程有序区的典型尺寸达到了传统显微镜和衍射工具（如透射电子显微镜、原子探针层析成像和x射线衍射）的分辨率极限。为了克服这一挑战，研究团队将采用一种新颖的、多管齐下的方法，结合理论建模（从头算密度泛函数理论计算、蒙特卡罗模拟和分子动力学）、冶金加工（制造和测试）和原子分辨先进结构表征技术（共振x射线散射、原位扫描电子显微镜和旋转扫描透射电子显微镜）。并将原子尺度上的短程有序特性与宏观尺度上的工程特性联系起来。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

It is well known that the ordering of atoms at the nanoscale dictates the properties and performance of materials, but knowledge of the quantitative relationships among properties, performance and structure - in particular the short-range ordering of atoms - is lacking for many structural alloys. Knowledge of these relationships has the potential to enable new high-strength, corrosion-resistant materials for use in transportation, energy, and infrastructure applications. This Designing Materials to Revolutionize and Engineer our Future (DMREF) award supports research to develop an improved fundamental understanding of short-range ordering, in order to identify guidelines for the design of new metallic materials with superior properties. Alloys with short-range order have characteristics of hard, but brittle intermetallics in the short-range, but also of soft pure metal or solid solutions, in the medium- to long-range. Despite classical understanding that suggests otherwise, there is increasing evidence that shows that short-range ordering can lead to unexpected improvements in mechanical properties. A short-range order-assisted alloy design concept will be explored as a new route to overcome the fundamental strength-toughness limitations in physical metallurgy. The overall goal of this research is to establish the fundamental understanding and the generic design rules that enable effective utilization of short-range order to realize damage-resistance in extreme environments. Concepts from this research are incorporated into educational modules in place at local science museums, and further educational benefits will stem from this work through the active participation of student researchers.This work aims to unravel what controls short-range order stabilities and characteristics, understand fundamentals of short-range order-assisted deformation micro/nano-mechanics, and design novel complex concentrated alloys that overcome current strength and toughness limits. It is necessary to understand how specific aspects of short-range order chemistry, size, and strength can be controlled, and how such variations would influence the interaction with dislocations. To this end, one of the most important challenges is regarding characterization. The typical size of the short-range ordered zones reaches the resolution limits of the conventional microscopy and diffraction tools such as the transmission electron microscopy, the atom probe tomography, and the x-ray diffraction. The research team will employ a novel, multi-pronged approach, combining theoretical modeling (ab-initio density functional theory calculation, Monte-Carlo simulation, and molecular dynamics), metallurgical processing (fabrication & testing), and atomically-resolved advanced structural characterization techniques (resonant x-ray scattering, in-situ scanning electron microscopy, and revolving scanning transmission electron microscopy) in order to overcome this challenge, and to link atomic-scale short-range order-characteristics to engineering properties at the macro-scale.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.