Density-based Thermodynamic Model and Open-Source Software for Quantitative Description of Interfacial Phase Behavior in Multi-Phase Multi-Component Alloy Systems

基于知识的工程合金设计需要对微观结构的每个和所有元素进行定量的热力学描述，从初级体相和次级相析出到微观结构缺陷，例如晶界和相界。虽然体相热力学已经建立并稳步发展，但微观结构缺陷的热力学描述和数据库还远远不够。在这个项目中，我们将开发一个强大的框架，用于计算基于可用的大量热力学数据的界面微观结构缺陷的热力学数据库和相图。我们将开发一个广义的多相、多组分密度模型，增强了弹性能的考虑（对于间隙原子）和一个非均相成核模型，以解决多相、多组分合金系统中的缺陷工程。结合这些理论的发展，将开发一个用于计算缺陷热力学和动力学的开源软件包。最终的开源软件将使用现有的基于calphad的批量热力学数据库作为输入，并计算界面缺陷的热力学性质、相图及其时间演化。本文将通过研究几种趋势铝合金的晶界析出和无析出带的形成来检验我们的广义模型和软件包的应用。通过研究广泛的成分和温度空间，我们将建立合金名义成分与各种铝合金热处理及其界面相变化之间的系统关系。本文将提出合金和工艺设计的策略，以减轻铝合金的界面破坏。随着缺陷工程研究的日益深入，本课题的目标是在微观结构缺陷计算热力学方面取得突破性进展。基于密度的广义模型和软件将为解决微观结构缺陷相行为量化的新需求提供有力的工具。该软件的输出可以指导基于知识的界面缺陷工程，并提供calphad兼容的数据库，这对于数据驱动的微观结构设计方法是必要的。

Knowledge-based design of engineering alloys requires quantitative thermodynamic descriptions of each and all elements of microstructure, from primary bulk phase and secondary-phase precipitates to microstructure defects, e.g., grain boundaries and phase boundaries. While thermodynamics of bulk phases are well established and steadily developing, thermodynamic descriptions and databases for the microstructure defects are far less explored. In this project, we will develop a robust framework for computing thermodynamic databases and phase diagrams for interfacial microstructure defects based on available bulk thermodynamic data. We will develop a generalized multi-phase, multi-component density-based model enhanced with elastic energy considerations (for interstitial atoms) and a heterogeneous nucleation model to address defects engineering in multi-phase multi-component alloy systems. Coupled with these theoretical developments, an open-source software package for computing defects’ thermodynamics and kinetics will be developed. The ultimate open-source software will use available CALPHAD-based bulk thermodynamic databases as inputs and compute thermodynamic properties, phase diagrams and their temporal evolution of the interfacial defects. The applications of our generalized model and the software package will be examined by studying grain boundary precipitation and the formation of precipitate-free zones in several trending aluminum alloys. By studying a wide range of composition and temperature spaces, we will construct a systematic relationship between alloy nominal composition and thermomechanical treatments of various Al alloys with their interfacial phase changes. Strategies for alloy and processing designs will be proposed to mitigate interfacial failure in aluminum alloys. Along with the increasingly advancing researches on defects engineering, the current project aims at a break-through development in computational thermodynamics of the microstructure defects. The generalized density-based model and software will provide powerful tools to address the emerging needs in quantifying the phase behavior of microstructure defects. The outputs of the software can guide knowledge-based engineering of interfacial defects and provide CALPHAD-compatible databases, necessary for data-driven approaches to microstructure design.