Thermodynamics and Kinetics of Structural Transformations in Metal and Ceramic Systems

金属和陶瓷系统结构转变的热力学和动力学

• 批准号: 0242619
• 负责人: Armen Khachaturyan
• 金额: $ 50.8万
• 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: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0242619&HistoricalAwards=false
• 关键词: Thermodynamics; Kinetics; Structural; Transformations; Metal

This award supports theoretical and computational research and education on the 3-dimensional evolution of strain-generating complex structures formed in diffusional and diffusionless transformations as well as of the evolution of defects, e.g. dislocations and cracks, formed in plastic deformation and fracture. In spite of an apparent diversity of these problems, there is a profound commonality among them: they present different aspects of the problem of self-organization of a multi-mode complex system with a long-range strain-induced anisotropic interaction. The Phase Field Microelasticity model developed by the PI together with 3-dimensional computer simulations will be used to investigate complex microstructures to elucidate the mechanisms controlling their evolution in technologically important systems. The relative role played by thermodynamics, crystallographic symmetry, microelasticity, and kinetics in microstructure evolution will be investigated to provide insight into mechanisms of thermal stability of microstructure, to predict the morphology and evolution rate, and to help establish the optimal processing parameters to yield microstructures that provide the best mechanical properties. Three groups of problems of scientific and engineering interest for advanced materials will be addressed. The first group, related to mechanisms controlling coherent decomposition in cubic systems with several structural variants of ordered intermetallics, includes investigating the formation of coherent two-phase microstructures with a very complex morphology (e.g., the chessboard microstructure in Co-Pt and other alloys) via precipitation of multi-variant ordered intermetallics from a transient congruently ordered phase, and investigating the formation of a multi-phase coherent microstructure involving more than two phases. The second group of problems involves the response of the martensite to applied stress in crystallographically and elastically inhomogeneous systems. This group includes the study of martensitic transformations involving dislocation plasticity. Stress-accommodating dislocations drastically affect the morphology of martensitic crystals; they are responsible for irreversible plastic deformation, which are detrimental to the Shape Memory Effect. The study of stress-induced martensitic transformation generated by advancing cracks in transforming inclusions is also included in this group. Of particular interest is the heterogeneous nucleation of the martensite followed by the rearrangement of its domains in the crack tip zones as well as the effect of this rearrangement on the development of the crack system. The corresponding stress-strain curve will be simulated. The third group of problems involves coherent diffusional and martensitic phase transformations near free surfaces. The study of these phenomena becomes possible because of the availability of a new theoretical approach developed with NSF support. Effective software that will enable realistic simulations of multiple processes simultaneously occurring in complex materials systems will be developed. The code will be distributed to researchers in the field. The galleries of virtual experiments, simulation animations and movies will be collected for public education in materials science and engineering. This activity will also enable more students to participate in advanced interdisciplinary research. There are additional broader impacts in the education of undergraduate and graduate students.%%%This award supports theoretical and computational research and education on the evolution of strain-generating complex structures formed in diffusional and diffusionless transformations as well as of the evolution of defects, e.g. dislocations and cracks, formed in plastic deformation and fracture. The Phase Field Microelasticity model developed by the PI together with 3-dimensional computer simulations will be used to investigate complex microstructures to elucidate the mechanisms controlling their evolution in technologically important systems. Microstructure plays an important role in determining mechanical properties of materials and in materials processing. Research focuses on three problem areas: The first is related to mechanisms controlling coherent decomposition in cubic systems with several structural variants of ordered intermetallics; The second is related to the response of martensite to applied stress in crystallographically and elastically inhomogeneous systems; The third involves coherent diffusional and martensitic phase transformations near free surfaces. Effective software that will enable realistic simulations of multiple processes simultaneously occurring in complex materials systems will be developed. The code will be distributed to researchers in the field. The galleries of virtual experiments, simulation animations and movies will be collected for public education in materials science and engineering. This activity will also enable more students to participate in advanced interdisciplinary research. There are additional broader impacts in the education of undergraduate and graduate students.***

该奖项支持在扩散和无扩散转变中形成的应变生成复杂结构的三维演变以及在塑性变形和断裂中形成的缺陷（例如位错和裂纹）的演变的理论和计算研究和教育。 尽管这些问题有明显的多样性，但它们之间有一个深刻的共同点：它们呈现了具有长程应变诱导各向异性相互作用的多模复杂系统自组织问题的不同方面。PI开发的相场微弹性模型与三维计算机模拟将用于研究复杂的微观结构，以阐明控制其在技术上重要的系统中演变的机制。热力学、晶体学对称性、微弹性和动力学在微观结构演化中所起的相对作用将被研究，以深入了解微观结构的热稳定性机制，预测形态和演化速率，并帮助建立最佳工艺参数以产生提供最佳机械性能的微观结构。三组先进材料的科学和工程利益的问题将得到解决。第一组，与控制具有有序金属间化合物的几种结构变体的立方系统中的相干分解的机制有关，包括研究具有非常复杂形态的相干两相微结构的形成（例如，Co-Pt和其它合金中的棋盘状微观结构），并研究了涉及多于两相的多相共格微观结构的形成。第二组问题涉及到马氏体在晶体学和弹性非均匀系统中对外加应力的响应。这一组包括对涉及位错塑性的马氏体相变的研究。应力调节位错严重影响马氏体晶体的形态;它们负责不可逆的塑性变形，这对形状记忆效应是有害的。应力诱发马氏体相变的研究也包括在这一组中。特别令人感兴趣的是马氏体的非均质成核，随后在裂纹尖端区域中其域的重排以及这种重排对裂纹系统的发展的影响。将模拟相应的应力-应变曲线。第三组问题涉及自由表面附近的相干扩散和马氏体相变。这些现象的研究成为可能，因为一个新的理论方法开发与NSF的支持。将开发有效的软件，使复杂材料系统中同时发生的多个过程的逼真模拟成为可能。该代码将分发给该领域的研究人员。 收集虚拟实验、模拟动画和电影的画廊将用于材料科学和工程的公众教育。这项活动也将使更多的学生参与先进的跨学科研究。 对本科生和研究生的教育还有更广泛的影响。%该奖项支持在扩散和无扩散转变中形成的应变生成复杂结构的演变以及在塑性变形和断裂中形成的缺陷（例如位错和裂纹）的演变的理论和计算研究和教育。PI开发的相场微弹性模型与三维计算机模拟将用于研究复杂的微观结构，以阐明控制其在技术上重要的系统中演变的机制。显微组织在决定材料的力学性能和材料加工过程中起着重要的作用。研究集中在三个问题领域：第一个是有关的机制控制相干分解立方系统与几个结构变体的有序金属间化合物;第二个是有关的马氏体的反应，在晶体学和弹性不均匀的系统中施加的应力;第三个涉及相干扩散和马氏体相变附近的自由表面。将开发有效的软件，使复杂材料系统中同时发生的多个过程的逼真模拟成为可能。该代码将分发给该领域的研究人员。 收集虚拟实验、模拟动画和电影的画廊将用于材料科学和工程的公众教育。这项活动也将使更多的学生参与先进的跨学科研究。 对本科生和研究生的教育也有更广泛的影响。