Virtual Melting and Amorphization as Mechanisms of Plastic Flow, Fracture, and Phase Transformations

虚拟熔化和非晶化作为塑性流动、断裂和相变的机制

• 批准号: 0969143
• 负责人: Valery Levitas
• 金额: $ 30万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0969143&HistoricalAwards=false
• 关键词: Virtual; Melting; Amorphization; Mechanisms; Plastic

This proposal addresses the new phenomenon of crystal-crystal phase transformation and amorphization that can occur through virtual melting at temperatures significantly below (1000K) the melting temperature. Some indications were found that virtual melting may serve as mechanisms of various structural changes: plastic flow under high strain rate loading of metals and metallic nanowires, fracturing, and sublimation. The objective of this project is to develop multiple theoretical and computational approaches (coupled to experiment) to study the main features of virtual melting, and to explore the generality of the phenomena in various applications. General continuum thermodynamic and kinetic theories, as well as phase field theory and quantitative models, will be developed and applied to simulations of phase transformations, plastic flow under high strain-rate loading, fracture, and sublimation via virtual melting. Molecular dynamics simulations for the same phenomena and materials will be performed. New mechanisms related to virtual melting are expected in various material systems, e.g., for phase transformation in HMX explosive, pharmaceuticals, and commercial nonlinear optical media and for high-pressure amorphization in geological, electronic, and superhard materials. Understanding the mechanism-based kinetics will lead to ability to control the transformations and look for hidden phases that need to be accessed (or avoided). One graduate student will be trained. Intense interdisciplinary collaboration will be developed. The PI will develop a new graduate course on multiscale modeling of phase transformations (available via distance learning) and will organize symposia devoted to the phase transformations.

该提案解决了在远低于（1000K）熔化温度的温度下通过虚拟熔化可能发生的晶体-晶体相变和非晶化的新现象。 一些迹象表明，虚拟熔化可能是各种结构变化的机制：金属和金属纳米线高应变率负载下的塑性流动、断裂和升华。该项目的目标是开发多种理论和计算方法（与实验相结合）来研究虚拟熔化的主要特征，并探索该现象在各种应用中的普遍性。将开发通用连续介质热力学和动力学理论，以及相场理论和定量模型，并将其应用于相变、高应变率载荷下的塑性流动、断裂和虚拟熔化升华的模拟。将对相同现象和材料进行分子动力学模拟。与虚拟熔化相关的新机制预计会出现在各种材料系统中，例如 HMX 炸药、药品和商业非线性光学介质中的相变，以及地质、电子和超硬材料中的高压非晶化。了解基于机制的动力学将有助于控制转变并寻找需要访问（或避免）的隐藏阶段。将培训一名研究生。将开展紧密的跨学科合作。 PI 将开发一门关于相变多尺度建模的新研究生课程（可通过远程学习获得），并将组织专门讨论相变的研讨会。