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.

技术摘要：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。具有先进技术特性的绝大多数材料是非平衡系统。当材料处于亚稳态或瞬时状态时，通常会获得它们最有价值的特性，并且其结构是结构和成分不同阶段的连贯的纳米级混合物。机械，介电，磁性和其他特性及其对应用领域的响应很大程度上取决于微观结构的形态。未开发的结构状态通常在相图的非平衡扩展中“隐藏”。在复杂系统中期望这些状态具有几种不断发展的内部热力学参数，例如组成，晶格结构，远距离原子秩序，磁化，极化等。这些参数的典型放松时间通常非常不同，它们的驱动力是非线性的，并且它们的进化在多维相位空间中发展。在这些条件下，在这些参数的空间中有多种变换途径，导致一系列具有可能异常结构和特性的短暂性和可稳态状态。这项研究的重点是对在这些相位响应的相关状态的无序状态中的暂时性状态“隐藏状态”的结构和动力学访问的系统理论和计算研究，以及这些状态的响应，以及这些响应的响应，以这些状态的响应和这些响应的响应。拟议的理论研究将研究（i）转换沿途，通常很难提前预见到的平衡，（ii）通过实际的3D 3D计算模型来“引导”转换沿我们选择的途径沿我们选择的途径进行层压，即对内部参数的进化（（iii）的构图和相关性响应的构建，并构成了构图和相关性，并相互启动，并相称的是，相互群众相关的构建效果（相互启发），并且是相互接触的，并且是相互启发的，并且是相互群体的，并且是相互群体的构建范围（相互群众关系），并且是相关的（相互报道的），并且是相互群体的质疑（又有相关性的）。或实际上重要的通用金属合金和陶瓷系统，代表重要类别的多参数相变。这些系统是：具有巨大磁静脉的Fe-GA BCC合金以及极大的弹性软化，Fe-Cu和Cu-Mn合金具有沿进化路径的多个结构性状态，形成棋盘结构的系统以及铁电固体解决方案的系统，根据Gibbs相位统治的组合，将其分解成均匀的组合，这些固定的组合形成了均匀的组合，并且必须将其组成均不同。极性域。后者是以前从未研究过的领域。将开发将在复杂材料系统中启用多个过程的现实3D模拟的软件。该代码将分发给该领域的研究人员。 PI将在高级本科和研究生级别开发一个新的课程“高级材料的理论和计算建模”，该课程将基于研究。非技术摘要：该奖项支持理论和计算材料理论和教育，重点是不处于平衡状态，却持续很长时间。这些材料的结构的长度比原子的结构大于原子的结构，但仍比拇指的大小要小得多，在确定其特性和可用的途径中起着重要的作用。 PI将使用理论和计算方法研究各种可以产生具有有趣且技术上有用的磁性和结构特性的合金的两元素系统。在这些系统中，结构，磁性和其他特性可能会链接在一起，以便改变一种特性的影响也可能会改变其他特性。这是研究将捕获的重要方面。这项研究对凝结物理学以及材料科学和工程有潜在的影响。对材料和材料处理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界。 PI将在高级本科和研究生级别开发一个新的课程“高级材料的理论和计算建模”，该课程将基于研究。