Modelling Phase Ordering Kinetics in Alloys

合金相有序动力学建模

• 批准号: 9520923
• 负责人: Bulbul Chakraborty
• 金额: $ 16.5万
• 依托单位: Brandeis University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-07-01 至 1999-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9520923&HistoricalAwards=false
• 关键词: Modelling; Phase; Ordering; Kinetics; Alloys

9520923 Chakraborty Kinetics of ordering in alloys will be investigated using models based on descriptions of the electronic structure of metallic alloys. By predicting microstructures and growth laws, these studies will provide the opportunity of making quantitative comparisons between theory and experiment. The type of modeling will also bridge the gap between experiments and theoretical results obtained using kinetic Ising models and their continuum version, the time-dependent Ginzburg-Landau model. The microscopic models of alloys have two features which make the study of growth kinetics relevant and interesting. The models include a description of the coupling between elastic strains and chemical order and they include typical metallic interactions such as Osize-effectO terms and long- range interactions arising from Fermi surface effects. Two types of models will be considered in the current work. One is a particular version of the embedded atom approach which provides a very good description of non-transition metal alloys, and the other is a model based on the direct pair- correlation function of alloys which can be calculated from the coherent potential approximation to disordered alloys. The latter approach is known to provide an excellent description of transition metal alloys and particularly of any fermi-surface realted effects. The study of kinetics can be divided into three separate parts: (1) direct Monte Carlo simulations of embedded atom Hamiltonians including chemical and displacement effects, (2) simulations of Langevin equations based on Ginzburg- Landau functionals constructed from microscopic models,and (3) studies of a generalized Ising model which provides the simplest model of ordering accompanied by a structural transition. The generalized Ising model has a wider range of applicability than alloys and will provide a description of kinetics in any system where there is a coupling between a structural distortion and some orderi ng field. %%% Theoretical research will be conducted on the properties of metallic alloys. In particular, studies will be made on how the components of a binary alloy mix together to form various phases and structures. Understanding how these phases evolve will contribute to predicting the properties of these alloys and how various processing paths affect these properties. ***

9520923 Chakraborty 将使用基于金属合金电子结构描述的模型来研究合金有序动力学。 通过预测微观结构和生长规律，这些研究将为理论与实验之间进行定量比较提供机会。 这种建模类型还将弥合实验与使用动力学 Ising 模型及其连续体版本（时间相关的 Ginzburg-Landau 模型）获得的理论结果之间的差距。 合金的微观模型有两个特征，使生长动力学的研究变得相关且有趣。 这些模型包括对弹性应变和化学顺序之间耦合的描述，并且包括典型的金属相互作用，例如 Osize 效应项和费米表面效应引起的长程相互作用。 当前的工作将考虑两种类型的模型。 一个是嵌入原子方法的特定版本，它提供了对非过渡金属合金的非常好的描述，另一个是基于合金的直接配对相关函数的模型，可以从相干势近似到无序势来计算合金。 众所周知，后一种方法可以很好地描述过渡金属合金，特别是任何费米表面相关效应。 动力学研究可以分为三个独立的部分：（1）嵌入原子哈密顿量的直接蒙特卡罗模拟，包括化学和位移效应，（2）基于微观模型构建的金兹堡-朗道泛函的朗之万方程模拟，以及（3） ）对广义伊辛模型的研究，该模型提供了伴随结构转变的最简单的排序模型。 广义伊辛模型比合金具有更广泛的适用性，并且将提供结构畸变和某些有序场之间存在耦合的任何系统的动力学描述。 %%%对金属合金的性能进行理论研究。 特别是，将研究二元合金的成分如何混合在一起形成各种相和结构。 了解这些相如何演变将有助于预测这些合金的性能以及各种加工路径如何影响这些性能。 ***