Thermodynamics and Kinetics of Phase Transformations in Complex Non-Equilibrium Systems

复杂非平衡系统相变的热力学和动力学

• 批准号: 0704045
• 负责人: Armen Khachaturyan
• 金额: $ 38.1万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0704045&HistoricalAwards=false
• 关键词: Thermodynamics; Kinetics; Phase; Transformations; Complex

TECHNICAL SUMMARY:This award supports theoretical and computational materials theory and education with a focus on non-equilibrium systems. The great majority of materials with advanced technological properties are non-equilibrium systems. Their most valuable properties are usually obtained when a material is in a metastable or transient state and its structure is a coherent nano-scale mixture of structurally and compositionally different phases. The mechanical, dielectric, magnetic, and other properties and their responses to the applied fields strongly depend on the microstructure morphology. Unexplored structural states are usually "hidden" in the nonequilibrium extension of the phase diagram. These states are expected in complex systems with several evolving internal thermodynamic parameters such as composition, crystal lattice structure, long-range atomic order, magnetization, polarization, and etc. A typical relaxation time for these parameters is usually very different, their driving forces are non-linearly coupled, and their evolution develops in a multidimensional phase space. Under these conditions, there are multiple transformation pathways in the space of these parameters leading to a succession of transient and metastable states with potentially unusual structures and properties.The focus of this research is on a systematic theoretical and computational study of the structural and kinetic accessibility of transient states "hidden" in the nonequilibrium part of the phase diagram and the response of these states to the applied field describing the structure-property relations. The proposed theoretical research will study (i) the succession of transformations along the way to the equilibrium that is often difficult to foresee in advance, (ii) the ways of "channeling" transformation cascades along the pathways of our choice by a realistic 3D computational modeling of the evolution of the internal parameters, (iii) the structure-property relations the response of the transient and metastable states to the applied fields, and (iv) the conceptually or practically important generic metal alloys and ceramic systems that represent important classes of multi-parametric phase transformations. These systems are: Fe-Ga bcc alloys with giant magnetostriction and an exceptionally large elastic softening, the Fe-Cu and Cu-Mn alloys with multiple structural states along the evolution path, the systems forming the checkerboard structures, and the ferroelectric solid solutions that, according to the Gibbs phase rule, have to decompose into a coherent mixture of different ferroic phases with a formation of complex assemblages of structural and polar domains. The latter is the area that has never been previously investigated.The software that will enable realistic 3D simulations of multiple processes in complex materials systems will be developed. The code will be distributed to the researchers in the field. The PI will develop a new course "Theoretical and Computational Modeling of Advanced Materials" at senior undergraduate and graduate levels that will be based on the research. NON-TECHNICAL SUMMARY:This award supports theoretical and computational materials theory and education with a focus on materials that are in not in equilibrium but are in states that last for a very long time. The structure of these materials on length scales larger than that of an atom but still much smaller than the size of a thumb plays an important role in determining their properties and the pathways available to the processing of these materials. The PI will use theoretical and computational methods to study various prototype two-element systems that can yield alloys with interesting and technologically useful magnetic and structural properties. In these systems, structural, magnetic, and other properties may be linked together so that effects that change one property may change others as well. This is an important aspect that will captured by the research. The research has potential impact on condensed matter physics as well as materials science and engineering. The potential broad impact on materials and materials processing contributes to the effort to keep America competitive.The computer simulation software that is developed in the course of the research will be distributed to the broader materials research community. The PI will develop a new course "Theoretical and Computational Modeling of Advanced Materials" at senior undergraduate and graduate levels that will be based on the research.

技术综述：该奖项支持理论和计算材料理论和教育，重点是非平衡系统。绝大多数具有先进工艺性能的材料都是非平衡体系。它们最有价值的性质通常是当一种材料处于亚稳态或瞬变状态，其结构是由结构和成分不同的相组成的纳米级相干混合物时获得的。材料的力学、介电、磁学等性能及其对外加电场的响应强烈依赖于微结构形态。未探索的结构状态通常被“隐藏”在相图的非平衡扩展中。这些态通常存在于具有多个内部热力学参数的复杂系统中，如组成、晶格结构、原子长程有序、磁化强度、极化等。这些参数的典型驰豫时间通常非常不同，它们的驱动力是非线性耦合的，它们的演化是在多维相空间中发展的。在这些条件下，这些参数的空间中存在多条转变路径，从而导致一系列具有潜在异常结构和性质的暂态和亚稳态。本研究的重点是对隐藏在相图非平衡部分的暂态的结构和动力学可达性以及这些状态对描述结构-性质关系的外加电场的响应进行系统的理论和计算研究。拟议的理论研究将研究(I)在通往平衡的过程中通常难以预先预见的相变的连续，(Ii)通过对内部参数的演变进行真实的3D计算建模，沿着我们选择的路径进行“沟道”相变的方式，(Iii)结构-性质关系，即瞬态态和亚稳态对外加电场的响应，以及(Iv)概念上或实践上重要的通用金属合金和陶瓷系统，它们代表了重要的多参数相变类别。这些系统是：具有超磁致伸缩和极大弹性软化的Fe-Ga体心立方合金，沿演化路径具有多种结构状态的Fe-Cu和Cu-Mn合金，形成棋盘结构的系统，以及根据Gibbs相律必须分解成不同铁相的共格混合物，形成结构和极性域的复杂组合的铁电固溶体。后者是以前从未研究过的领域。将开发能够对复杂材料系统中的多个过程进行逼真3D模拟的软件。代码将被分发给现场的研究人员。该研究所将在这项研究的基础上，在高年级本科生和研究生水平上开发一门新的课程--《先进材料的理论和计算建模》。非技术概述：该奖项支持理论和计算材料理论和教育，重点关注处于非平衡状态但处于持续很长时间的材料。这些材料在长度尺度上的结构比原子大，但仍然比拇指小得多，在决定它们的性质和加工这些材料的途径方面发挥着重要作用。PI将使用理论和计算方法来研究各种原型双元素系统，这些系统可以生产出具有有趣的和技术上有用的磁性和结构性能的合金。在这些系统中，结构、磁性和其他性质可以链接在一起，从而改变一种性质的效果也可以改变其他性质。这是研究将捕捉到的一个重要方面。这项研究对凝聚态物理以及材料科学和工程都有潜在的影响。对材料和材料加工的潜在广泛影响有助于保持美国的竞争力。在研究过程中开发的计算机模拟软件将分发给更广泛的材料研究社区。该研究所将在这项研究的基础上，在高年级本科生和研究生水平上开发一门新的课程--《先进材料的理论和计算建模》。