Computational diffusion kinetics and its applications in study and design of rare metallic materials

Computational diffusion kinetics(CDK),with a spirit of and being coupled with the computational thermodynamics(CT,or called as the CALPHAD technique),plays increasingly important role in the alloy design/optimization and microstructure control during the processing of advanced metallic materials.This paper is to highlight recent progress of CDK in research with great focus on novel Ti and Zr alloys,which was largely performed in the authors’group.It ends with one representative example of the applications of CDK,coupled with CT,quantitative phase field,and three-dimensional(3D)statistical calculation,in designing the heattreatment schedule for the dual phase(αβ)Ti–6Al–4V alloys.     

CALPHAD modeling of molar volume

Databases concerning basic physical properties of materials, such as molar volume, density, thermal expansion coefficient, elastic constants, thermal conduc- tivity, etc., are essential parts of the underlying knowledge for materials design. While thermodynamic databases provide chemical driving forces and phase equilibrium data, physical property databases provide essential physical parameters, such as volume, lattice constant, lattice misfit, elastic energy, interfacial energy, etc., for phase transfor- mation and microstructure simulations. Combined with thermodynamic databases, physical property databases established on the basis of the calculation of phase diagram （CALPHAD） method can be used to calculate physical properties together with phase equilibria, phase fractions, phase compositions, and thermodynamic properties for multi-component and multi-phase material systems and for the constituent phases. In this paper, we will discuss in detail various volume models based on the CALPHAD method which are capable of describing experimental data in a wide range from cryogenic temperatures to melting points, from the atmospheric pressure to high pressures for pure substances as well as multi-component and multi- phase materials.     

The materials genome and CALPHAD

The mapping of the human genome is an important basis for the development of new medicals and medical treatments.Consequently,it has attracted tremendous research funding over the last decade.On June2011,the Materials Genome Initiative was announced by the US President Obama as collaboration on modeling and advanced materials databases.Unfortunately,the materials genome was given a rather vague definition in the announcement.However,the materials genome should be defined in analogy with biological genomes and one may then conclude that:at any moment,the performance of a specific material depends on its chemical composition(inherent property stored in its genome)and its environment(external interactions–processing–conditions during usage).The materials genome should thus be defined as a set of information encoded in the language of thermodynamics obtained by careful assessment of experimental data and quantum mechanical calculations from which certain conclusions about the material can be drawn.The CALPHAD databases contain the thermodynamic and kinetic properties of a materials system.Such databases allow the prediction of materials structure as well as its response to processing and usage conditions,and are major parts of integrated computational materials engineering.     

Development and application of phase diagrams for Li-ion batteries using CALPHAD approach

Phase diagrams provide fundamental knowledge about design map of new electrode materials for Li-ion batteries. The CALPHAD (CALculation of PHAse Diagrams) approach is widely applied to the development of phase diagrams and property diagrams in a thermodynamic language. Within the CALPHAD framework, the theoretical modeling can be performed to predict phase equilibria, thermodynamics, electrochemical and physical properties of electrodes. This review provides the successful application of high quality calculated phase diagrams and thermodynamic property diagrams in CALPHAD investigation to both cathodes and anodes of Li-ion batteries, including Li–Co–O, Li–Ni–O, Li–Co–Ni–O, Li–Mn–O, Li–Cu–O, Li–Si, Li–Sb and Li–Sn systems with. The intensive CALPHAD-type research may also predict electrochemical properties, cell performance of the Li-ion batteries to achieve more efficient development of electrode materials.     

多尺度材料计算方法

 在材料基因组科学研究中,多尺度集成材料计算占有不可或缺的地位。本文以微观-介观-宏观材料计算方法中具有代表性的第一原理、分子动力学、计算热力学/动力学及有限元方法为重点,介绍多尺度材料计算方法的基础和应用。     

冶金热力学计算软件的开发

在冶金热力学研究中,一般会碰到很多热力学数据及其计算分析,为快速精确地进行热力学计算,利用VC＋＋语言的计算功能,研制了基于数据库信息的冶金热力学计算软件。软件数据库中存储了冶金研究中常用物质的热力学性质参数供用户使用并且该数据库可根据用户的需求进行扩充。用户可利用数据库中热力学数据进行冶金过程反应的热力学计算,得到如反应吉布斯自由能、反应热及反应平衡常数等基本热力学参数并将计算结果生成数据文件作为绘图软件的输入。     

相图计算及其在无铅焊接材料中的应用

随着Sn-Pb焊接材料在电子工业中的应用限制,无铅焊接材料的设计与开发已经是电子封装领域的重要课题.相图计算方法(CALPHAD)作为一种科学研究方法也越来越多的应用到材料的设计开发和工艺研究方面.相图计算主要是依据实验数据,建立热力学模型,根据Gibbs自由能最小原理计算相平衡.主要介绍了相图计算原理,以及根据已经评估的热力学数据,相图计算方法在无铅焊接材料的设计开发、焊接过程的界面反应、焊接凝固模拟等方面的应用.     

Simulation of mesoscale interfacial properties using the lattice Boltzmann method

We derive the mesoscopic interparticle potentials from macroscopic thermodynamics for van der Waals, Redlich-Kwong, and Redlich-Kwong-Soave equations of state and find that all these potentials are very similar to the Lennard-Jones potential. To in-vestigate the interfacial property at the mesoscale level, we incorporate free energy functions into the single-component multiphase lattice Boltzmann model and obtain the saturated density coexistence curves and interface mass density profiles across the interface using this method with different equations of state. The simulation results accurately reproduce the properties of equilibrium thermodynamics. Numerical results for single-component phase transitions indicate that a bubble-growth process is obtained and the equilibrium phase diagram is achieved at a given temperature. Bulk free energy, the interfacial energy coefficient, and other properties of nonequilibrium thermodynamic parameters, which are used to examine interfacial properties, are obtained in these simulations, and all these parameters are found to obey irreversible thermodynamics.     

EuCl3-CaCl2二元系的热力学优化和计算

引入短程有序-扩展似化学模型来描述EuCl3-CaCl2二元体系液相的Gibbs自由能,根据实验测定的相图和混合焓数据,运用CALPHAD技术对该体系进行了热力学优化和计算,优化计算的结果和实测值符合很好.     

化学气相渗透工艺制备陶瓷基复合材料

综述了采用化学气相渗透(chemical vapor infiltration, CVI)工艺制备陶瓷基复合材料(ceramic matrix composites, CMCs)的模拟与可视化、柔性与鲁棒性以及强韧性控制与设计等研究的进展和趋势. 陶瓷基复合材料气相制造过程模拟涉及气体传输、反应热力学与动力学、预制体的孔隙结构建模等理论, 是一个典型的多尺度和多物理场问题. 运用量子化学、化学热力学、微观动力学、有限元、水平集和人工智能等方法, 实现了复合材料致密化过程的模拟和成分分析, 更加精准地反映了气体在多孔预制体中的各向异性传输和沉积过程, 为工艺优化提供更准确的控制参数. CVI工艺制备陶瓷基复合材料具有柔性与鲁棒性等工艺特性, 包括应用广泛性, 可控制、可调整与可设计性, 可连接与可组装性, 可纠错、可修复与可兼容性等诸多特性, 适用于陶瓷基复合材料微结构的调控, 是陶瓷基复合材料领域最先进的基础制造方法. 陶瓷基复合材料的强韧性一直是其发展中的核心问题, 增强体纤维、基体及二者界面之间的模量匹配, 以及热残余应力和纤维基体体积分数等参数的设计与控制是这个核心问题的关键. 通过合理控制与设计这些参数, 可以实现陶瓷基复合材料的强韧化控制与设计, 从而适应不同使用环境条件的需求.     

基于“材料基因组工程”的3种方法在镍基高温合金中的应用

"材料基因组工程"强调以产业应用为导向,集成和发展材料的计算工具、试验工具和数据库等核心基础能力,聚焦解决关系国计民生产业应用中材料的关键问题。本文列举3种基于"材料基因组工程"方法在镍基高温合金中的实际应用,包括高通量合金制备及其关键热力学和动力学数据的高通量采集、显微组织的多尺度和多维度表征、微型试样的力学性能检测。分析表明,定量预测和描述材料成分、工艺、组织和性能关系的计算、表征和数据库技术面临极大挑战,基于"材料基因组工程"的方法将促进镍基高温合金的研发,加快从实验室研究到市场应用的转化。     

流体间界面张力的热力学研究进展(非表面活性剂体系)

流体间的界面张力是石油工业、化工、湿法冶金及环境保护等领域中重要的基础数据。界面现象的统计力学研究已取得了很大的发展。文中介绍了近年来国内外在非表面活性剂体系界面张力的热力学研究方面的进展 ,主要包括如下 3个方面 :非表面活性剂体系界面张力的数据来源 ;界面张力的热力学研究 ,强调了泛函理论和微扰理论的应用 ;分子模拟方法在界面张力研究中的应用。     

Perspective on Materials Genome~

The author’s perspective on Materials Genome is presented in this paper through several related projects.Current thermodynamic and kinetic databases of multicomponent materials consist of Gibbs energy functions and atomic mobility of individual phases as functions of temperature,composition,and sometimes pressure,i.e.,with the individual phases based on crystal structures as the genome(building blocks)of materials.It is articulated that if an individual phase has its internal configurations,such as magnetic spin configurations and ferroelectric polarization,change significantly with respect to temperature,stress,and magnetic and electric fields,then those individual configurations instead should be considered as the genome of the individual phase.The‘‘mutation’’of an individual phase is governed by the entropy of mixing among the individual stable and metastable configurations,named as microstate configurational entropy,and responsible to anomalies in individual phases.Our ability to tailor the properties of those individual configurations as a function of compositions is the key for the design of materials.     

CALPHAD技术在稀土氯化物-碱土金属氯化物二元系相图中的应用

随着科学技术的不断发展,CALPHAD技术已经成为相图研究的一个非常重要的方法和手段．根据稀土氯化物一碱土金属氯化物二元系相图的实验数据,利用CALPHAD技术可以获得一系列热力学参数,这些热力学参数为稀土金属的冶炼工业生产提供了非常重要的指导．     

Microstructure-based multiphysics modeling for semiconductor integration and packaging

Semiconductor technology and packaging is advancing rapidly toward system integration where the packaging is co-designed and co-manufactured along with the wafer fabrication. However, materials issues, in par- ticular the mesoscale microstructure, have to date been excluded from the integrated product design cycle of electronic packaging due to the myriad of materials used and the complex nature of the material phenomena that require a multiphysics approach to describe. In the context of the materials genome initiative, we present an overview of a series of studies that aim to establish the linkages between the material microstructure and its responses by considering the multiple perspectives of the various mul- tiphysics fields. The microstructure was predicted using thermodynamic calculations, sharp interface kinetic models, phase field, and phase field crystal modeling techniques. Based on the predicted mesoscale microstruc- ture, linear elastic mechanical analyses and electromigra- tion simulations on the ultrafine interconnects were performed. The microstructural index extracted by a method based on singular value decomposition exhibits a monotonous decrease with an increase in the interconnect size. An artificial neural network-based fitting revealed a nonlinear relationship between the microstructure index and the average yon Mises stress in the ultrafine interconnects. Future work to address the randomness of microstructure and the resulting scatter in the reliability is discussed in this study.     

实时织物悬垂性能物理模型及应用

快速计算机模拟和仿真技术是纺织物、服装的计算机辅助设计和制造的关键技术组成．逼真的纺织物、布料、服装的三维计算机可视化设计在其他许多领域也非常重要．例如在3DCG电影制作中逼真的计算机服装动态特效、3D电脑游戏、网上购物等．本文着重于计算方法，综述和分析了服装物理模型及其应用的最新进展，探讨了当前主要存在的问题，技术挑战，和可能的解决方案．提出了一种基于变形能的服装悬垂模型及算法，并展示了仿真结果．本文所提出的模型适用于纺织物、服装的快速计算机三维动态模拟．另外，也提出和探讨了识别纺织物材料的复杂动态变形材料性能参数的可能性方案．     

压铸充型过程模拟并行搜索算法

压铸过程充型模拟技术存在的主要问题之一是迭代过程缓慢而导致计算效率较低。该文通过对压铸充型的数学模型和计算模型进行分析 ,利用机群计算平台 ,提出并建立了一种并行搜索计算模型。该模型在原有串行算法的基础上 ,通过效率参数的适当选择和调整 ,实现了利用并行计算优化串行过程的目的。这种算法可以充分发挥各个结点的计算能力 ,有效降低结点之间的通信时间。通过对实际压铸零件进行的计算测试表明 ,该算法在保证原有计算精度的前提下 ,可以在一定范围内极大地提高计算效率。     

DNA sequencing technology based on nanopore sensors by theoretical calculations and simulations

DNA sequencing based on nanopore sensors is a promising tool for third-generation sequencing technol- ogy because of its special properties, such as revolutionized speed and low cost. With about two decades of nanopore technology development, the pioneering work has dem- onstrated the ability of nanopores to perform single-mole- cule detection and DNA sequencing. However, the microscopic mechanisms of DNA transport dynamics through nanopores remain largely unknown. Currently, DNA microscopic transport in a nanopore is difficult to characterize and several unexpected experimental obser- vations are equivocal. This limitation can be resolved using theoretical calculations and simulations. These computa- tional methods can monitor the entire dynamic process that DNA undergoes in solution at a single-atom resolution that can accurately unveil the mystery of DNA transport dynamics and predict certain unexpected phenomena. This paper mainly reports the recent applications of computa- tional and simulation methods applied to the study of DNA transport through both biological and synthetic nanopores. We hope the theoretical calculations and simulations of DNA transport through nanopores can benefit the design of DNA sequencing devices.     

First-principles calculation of crystalline materials genome: a preliminary study

The US President Obama launched the Materials Genome Initiative on June 24,2011,aimed at speeding up the pace of discovering,developing,manufacturing,and deploying advanced materials by at least twice as fast as is possible at present,at a fraction of the cost with the help of existing advanced computer technology.According to the authors’understanding to the event,this article will first give a brief discussion on the origin of material genome,its scientific implication,research significance,and the far-reaching influence of materials genome study to the developments of materials science and human society.Then,the subsequent contents will introduce the research progresses of the related works carried out by the authors’research group over the last decade,on the first-principles studies of crystalline materials genome.The highlights are focused on the method implementations for configuration optimization of lattice structure,first-principles calculations of various physical parameters on elastic,electronic,dielectric,and thermodynamic properties,and simulations of phase transition and particle transport in solids.The technical details for extending these methods to low-dimensional crystalline materials are also discussed.The article concludes with an outlook on the prospect of materials genome research.     

LiBr-SrBr2二元体系的热力学优化和计算

运用CALPHAD(相图计算)技术对LiBr—SrBr2二元体系进行优化和计算,计算得到的共晶点为34．93％(摩尔百分比) SrBr2,709．20 K,化合物LiSr2Br5的转熔温度和组成分别为760．00 K和55．43％(摩尔百分比)SrBr2．从LiBr—SrBr2体系的实验数据出发,预报了该体系液相混合焓和混合熵,计算得到的结果与实验相图和热力学数据相吻合．