Experimental and Computational Thermodynamics of Some Ternary Transition Alloy Systems

技术支持：相图的热力学建模提供了一个机会，以更有效的方式接近合金发展的相平衡方面比实验确定在许多温度下的大量合金的相平衡。基本的方法是开发一个热力学描述的自由能的每一个阶段的组成和温度的函数，然后计算在给定的温度下的自由能的最小值为一个特定的组合物。用这种方法，相图可以在几分钟或几小时内绘制出来，而不是用实验方法测定相图所需的几个月。计算图的准确性取决于在相的自由能描述中使用的热力学数据的准确性。关于Al和Ni基合金系统的此类数据很少或不存在。由于这个原因，通常利用现有的相图来开发热力学模型。这样的模型可能不是唯一的，并且可能不能正确地反映系统的基本热力学。为了建立可靠的热力学模型，必须有一些关于系统的热力学数据。在本项目中，PI将确定一些三元铝镍基合金相和一些稀土B2相的形成热，包括具有实质成分范围的相的成分依赖性。使用定制的高温反应量热计测定生成热，其典型精度为+/-1kJ/mole。此外，差热分析将用于确定熔点和其他相变，差示扫描量热法将用于确定所选合金的热容作为温度的函数。DTA和DSC实验将在SETARAM 1750 C热量计中进行。改进后的数据库将被用来计算几个等温截面在每个三元合金系统使用Thermocalc。这些数据也将被用来验证各种外推模型从文献中预测的形成热的三元化合物从二元数据。非技术性：该项目将保持美国唯一的实验热力学组测量合金的形成热，并将提供在这一领域的培训，一个研究生和两个本科生。将建立和维持一个网络服务器，向国际社会提供世界各地最近实验热力学数据的单一来源。从实验中确定的数据将被用来开发一个改进的，自洽的热力学数据库的铝镍基合金与教授Bo Sundman，计算热力学部，皇家理工学院，斯德哥尔摩，瑞典和博士Evan Copland，美国宇航局，克利夫兰。

TECHNICAL: Thermodynamic modeling of phase diagrams provides an opportunity to approach the phase equilibria aspects of alloy development in a more efficient manner than experimentally determining the phase equilibria in large numbers of alloys at many temperatures. The basic approach is to develop a thermodynamic description for the free energy of each phase as a function of composition and temperature and then to compute the minimum in free energy for a particular composition at a given temperature. In this way the phase diagram can be mapped in a matter of minutes or hours rather than the months involved with experimental methods of phase diagram determination. The accuracy of the computed diagram is dependent on the accuracy of the thermodynamic data used in the free energy descriptions of the phases. Such data on Al and Ni-base alloy systems are scarce or non-existent. For this reason it is common to utilize an existing phase diagram for the development of the thermodynamic models. Such models may not be unique and may not correctly reflect the underlying thermodynamics of the system. For reliable thermodynamic models it is essential to have some thermodynamic data on a system. In this project the PI will determine the heats of formation of a number of ternary Aluminum-Nickel-base alloy phases and some Rare earth B2 phases including the composition dependence for phases with substantial composition ranges. The heats of formation are determined using a custom-built high temperature reaction calorimeter with a typical accuracy of +/-1kJ/mole. In addition differential thermal analysis will be used to determine melting points and other phase transitions and differential scanning calorimetry will be used to determine heat capacity of selected alloys as a function of temperature. The DTA and DSC experiments will be performed in a SETARAM 1750 C calorimeter. The improved database will be used to compute several isothermal sections in each of the ternary alloy systems using Thermocalc. The data will also be used to validate various extrapolation models from the literature for the prediction of heats of formation of ternary compounds from binary data. NON-TECHNICAL: This project will maintain the only US based experimental thermodynamics group measuring alloy heats of formation and will provide training in this field to one graduate and two undergraduate students. A web server will be set up and maintained which provides the international community with a single source of recent experimental thermodynamic data from around the world. The data determined from the experiments will be used to develop an improved, self-consistent thermodynamic database for Aluminum-Nickel-base alloys in collaboration with Professor Bo Sundman, Division of Computational Thermodynamics, Royal Institute of Technology, Stockholm, Sweden and Dr. Evan Copland, NASA, Cleveland.