相变热力学基础-第8章.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,材料设计与,计算热力学,第八章,1,2,8.1,热力学和材料设计,8.2 CALPHAD,的发展史,8.3 CALPHAD method,8.4 Calphad,的热力学模型,8.5 Calphad,软件和热力学数据库,8.6 Calphad,的应用实例,3,8.1,热力学和材料设计,材料设计（,materials by design,）一词正在变为现实，它意味着在材料研制与应用过程中理论的份量不断增长，研究者今天已经处在应用理论和计算来设计材料的初期阶段。,材料科学的计算与理论技术,美国国家科学研究委员会（,1995,）,4,已有大量可供参考的理论知识和近百年甚至数百年的经验数据。,计算技术的飞速发展，大大提高了人们对材料领域的所有可以量化认识进行定量计算的可能性。,材料的研究与开发终于可以走出尝试法（,Trial and error),阶段，进入新材料设计的初级阶段,与材料热力学关系最密切的标志是计算相图,CALPHAD,（,CALculation PHAse Diagrams,）领域的出现。,5,材料设计的定义之一：,相图计算（,Calphad),材料设计（,Materials by design,）,为满足预期材料的特性而用来确定材料的类型、材料,的成分及其加工处理制度的计算机程序系统。,包含各种数据库的建设,6,相图与材料设计的关系,Phase diagrams are visual representations of the state of a material as a function of temperature,pressure,and content of the constituent components,Phase diagrams are frequently used as roadmaps for alloy design or a better understanding of the processing of materials.,相图是现代材料设计的一个重要依据,7,相图的种类：,(1),实验相图,(Experimental phase diagrams):,利用各种试验方法,(,热分析法,热膨胀法、金相法等,),测定,缺点,:,费时、费力、成分难控；过高熔点；达平衡时间过长,.,现状：,二元相图，,2/3,已测；三元相图，,2%,已测,(2),理论相图,(Theoretical phase diagrams):,也称第一原理计算相图。是一种不需要任何参数，利用电子理论从头算起的理论计算相图。是人类相图研究的最高目标，目前还是在完善理论阶段。,只在少量二元和三元相图的计算方面对实际材料的设计有指导作用,8,(3),计算相图（,Calculated phase diagrams,）,:,也称热力学计算相图。是在严格的热力学原理的框架下，利用各种渠道获得的相关热力学参数计算的相图。,目前这种方法计算的相图不仅能很好地接受实验结果的检验，再现二元相图；而且热力学计算的方法还能够检验那些相差较远，互不一致的实验相图。,形成了一门新的介于热力学、相平衡和计算机科学之间的交叉分支学科：,CALPHAD,Computational Thermodynamics,相图可以被认为是该系统热力学性质的表征,9,计算相图与实验相图的区别：,计算相图在考虑了热化学信息的情况下，利用最小二乘法原理将误差减为最小的相图；而实验相图存在着各种误差，且不同的人测出的相图有较大的差异,;,计算相图使相图的各种表示形式成为可能，对多元系，可给出相图的任何所需截面图，这些是实验相图难以做到的。,计算相图可从低元热力学特征函数的参数外推高元体系的热力学性质及相图，可由实验易测或易测准部分来预测实验难测或难测准部分相图，绕过某些实验困难。,10,对于实际应用的二元或三元材料来说，材料成分设计参照现有的相图还比较方便。,真正完善的三元相图较少，四元或更多元系统的相图、相平衡信息更少。,获得优良新材料的一个重要方法是多元化,随着组元数增加，完全用实验方法测定相图工作量太大，而且相图的描述也很困难,Solution,？,11,Solution,CALPHAD,Computational Thermodynamics,材料设计热力学的核心内容：,对三元和更多元的系统，通过热力学方法计算出平衡的相成分、相体积分数,材料设计,12,8.2 Development of the CALPHAD Method,材料设计和制备的重要依据,:,相图,材料体系中各相的热力学参数,从理论上来说，热力学和相图之间的联系不存在任何障碍。,从历史上看，两者却是沿着各自的方向独立发展：,传统上，相图主要是用热分析、金相分析和,X,射线结构分析等实验方法测定，并没有用到热力学知识，也没有完全将热力学用来解决生产实际问题。,热力学则主要是对相平衡进行理论分析提出不同状态下平衡过程的方向和限度，其实验数据主要是热化学性质的测定。,13,随着溶液模型、数值方法和计算机软件等方面取得了较大的进展，这才使得人们能够将热力学应用到相图中来。,热力学和相图的计算机藕合形成了,CALPHAD,技术,14,19th century,:Gibbs-correlation between thermodynamics and phase equilibria,1908,:van Laar mathematical synthesis of a binary system,1929,:Hildebrand regular solution concept,1957,Meijering thermodynamic analysis of Cu-Cr-Ni,1963,:Hume-Rothery phase equilibria in Fe-base alloys,1970,:,Kaufman,and Bernstein foundation of CALPHAD,1972,:Mager least-squares method for optimization,1973,:1st CALPHAD Meeting,1977,:Lukas first computer software(Lukas Programs),1977,:1st volume of CALPHAD Journal,1981,:Agren,Hillert,Sundman,Compound Energy Formalism(,Sublattice Model),since 1985,:continuous development of models and software,15,主要材料热力学计算软件,(,数据库,):,PANDAT,FactSage,MTDATA,THERMO-CALC,16,CALPHAD,Journal of Alloys and Compounds,Journal of Phase Equilibria,Metallurgy and Materials Transactions(A and B),Acta materialia,Journal of Physics and Chemistry of Solids,Z Metallkde,JOM,Materials Science and Engineering A,Journals,17,CALPHAD,方法经过近,30,年的发展，是当今最成熟的一种相图计算,方法，也是目前惟一切实可行的相图热力学优化和评估的方法。,CALPHAD,方法：,根据所研究体系中各相的特点，集热力学性质、相平衡数据、晶体结构、磁性、有序,-,无序转变等信息为一体，建立描述体系中各相的热力学模型和相应的自由能表达式（其中的可调参数,(adjustable parameter),通过实测的热力学和相图数据，经过优化计算获得，或用各种经验方法估算）,最后基于多元多相平衡的热力学条件计算相图，以最终获得体系的具有热力学自洽性,(Thermodynamic consistency),的相图和描述各相热力学性质的优化参数,(optimized parameter),。,8.3 CALPHAD method,18,19,CALPHAD,Stable phase,diagram,Metastable phase,diagram,Volume fraction,of phase,Estimation of T0 lineThermodynamic property,Driving force,Chemical potential,20,8.5 Materials thermodynamics data and software,通过对某一相关多元系的各种类型的实测热力学数据的收集、比较、评估和优化，经过较长时间工作的积累，构筑为解决某一方面问题的材料热力学数据库或材料设计数据库,21,主要材料热力学数据库,(1)NBS/ASM,数据库（美国）,1977,年始建，主要内容有二元、三元合金相图集及其公报、手册；也开发在线合金相图数据库等。,(2)Manlabs,数据库（美国）,CALPHAD,创始者之一的,L.Koufman,主建,内容以陶瓷材料等无机物为主，形式为典型的,CALPHAD,模式。,(3)FACT,数据库（加拿大）,FACT(Facility for the Analysis of Chemical Thermodynamics,）包括纯物质和溶体的热力学性质数据，相图计算软件和热力学数据优化软件等。,(4)SGTE,数据库（欧洲）,目前在,CALPHAD,领域影响最大的材料热力学数据库。,20,多年前，在欧洲的七个实验室以,SGTE(Scientific Group Thermo-dataEurope),为名称建立的热力学数据库。,22,主要材料热力学计算软件,(,数据库,):,PANDAT,FactSage,MTDATA,THERMO-CALC,23,PANDAT,：,Automatically calculates stable phase diagrams for multicomponent phase diagrams without requiring starting values.It can also be used to estimate the microstructures under real casting conditions using Scheil and equilibrium simulations,including consideration of back diffusion.The software has been applied to calculation of multi-component Al-base,Mg-base,Ti-base and Fe-base alloys.,Polytechnique de Montreal and McGill University,Canada,is the result of a fusion of F*A*C*T,and ChemSage,each of which started over 25,years ago.It supports 11 different solution models,for databases covering 4400 compounds,3400,pure substances,(SGTE),a 19 component oxide,melt/glasses,with dilute solutions of nine additional,elemental and oxide species.The,SGTE,intermetallic,binary and ternary alloy databases with several hundred binary,ternary and quatemary alloy systems are also available.,25,MTDATA,www.npl.co.uk/mtdata/,MTDATA provides a range of modules,for calculating binary,ternary and multicomponent phase diagrams without,requiring starting values.It also contains 18 databases including aqueous,organic,salt,solder,III-V,oxide,slag,and,SGTE databases.These modules,and databases have been used in the analysis of a very wide range of,industrial problems including energy conversion,lamp chemistry,pollution control,hot and aqueous corrosion,coating,etching and crystal growth.,26,THERMO-CALC,a versatile tool to calculate binary,ternary and multicomponent phase diagrams for a wide range of materials with 22 thermodynamic databases.Thirteen different solution models can be used to describe a variety of systems.Integrated with mobility databases covering diffusion of 75 elements,the,DICTFU module(DICTRA)couples the,thermodynamic and kinetic computations to simulate a great number of practical problems including homogenization,carburizing,gradient sintering of carbide tool workpieces,Ostwald ripening and cooperative growth in dendrite and pearlite formation.,Royal Institute of Technology,，,Sweden,目前在,CALPHAD,领域影响最大的材料热力学计算软件,27,8.6 Examples of applications,CALPHAD,Stable phase,diagram,Metastable phase,diagram,Volume fraction,of phase,Estimation of T0 line,Thermodynamic property,Driving force,Chemical potential,28,Effect of Bi and In on the melting temperature,Calphad,在无铅焊料设计中的应用,29,Simulation of solidification,(Sn-2.0Ag-0.5Cu-7.5Bi alloy),30,Mass fraction of each element in liquid phase,31,Latent heat evolution during solidification,32,Cross-sectional view of the simulated soldering components,33,34,Prediction of first,-formation compound,phase in the Cu-Sn system,Driving force with respect to the phase equilibrium Liquid/fcc,Cu,6,Sn,5,Cu,3,Sn,35,Dissolution behavior of Cu substrate in the molten Sn(250,0,C),36,Comparison between the calculated and experimental results,Cu/Sn diffusion couple,Cu/Sn-3.5Ag diffusion couple,37,