Cu—Al 合金马氏体相变热力学

依据规则溶液模型,在充分利用 Cu-Al 系相图的基础上,导得 Cu-Al 合金的一些热力学参量。应用统计模型处理了 Cu-Al 合金中涉及马氏体相变的体心立方及面心立方两种结构的有序相变,直接从理论上计算了不同成分 Cu-Al 合金α和β相的平衡温度 T~*,有序α′与β′相的平衡温度 T_0,以及马氏体相变点 M_s,其中 M_s 与实验值非常吻合。计算还表明 Cu-Al 系中 T_0比 T_0~*更高。     

相图及其在钛电解新工艺和钛合金设计中的应用

相图是材料设计的指导书、冶金工作者的地图和热力学数据的源泉.简要概述了近年来相图计算研究的进展,举例说明了Ti-C-O三元系及其亚二元系相图在钛电解新工艺研究中的应用及Ti-Al相图在钛合金设计中的应用,并在文献中列出了新的可靠的合金和化合物相图的来源.最后指出,进一步测定Ti-C-O三元系中TiC-TiO固溶体的精确固溶范围及其与其它相的相关系对于直接电解TiO2提取金属钛新工艺的工业化有重要意义.     

低温区间的Fe-N二元相图理论分析

采用亚点阵的化合物能模型计算低温区间Fe-N二元相图。计算结果表明,25～350℃低温区,分别存在着α-Fe(N)和γ＇-Fe4N,γ＇-Fe4N和ε-Fe₂N_1-x二相平衡。α-Fe(N),γ＇-Fe₄N,ε-Fe₂N_1-x均为热力学稳定相。依据Guillermet和Du的热力学性质参数计算的低温区间Fe-N二元相图与现有实验数据相符。     

世界著名的“金氏相图测定法”的创立者中南大学教授、博士生导师中国科学院院士金展鹏

金展鹏男,1938年11月出生,广西荔浦人,中共党员,中南大学材料科学与工程学院教授,博士生导师。他早年投身于材料科学,20世纪70年代开始进行相图热力学和相变动力学的研究。他发展了结构特点不同的相的热力学模型和相图优化计算方法,构筑了一系列金属合金、氧化锆基陶瓷及人工晶体材料的相图。发展了研究相图等温截面和等温四面体的多元扩散偶方法,     

世界著名的“金氏相图测定法”的创立者 中南大学教授、博士生导师 中国科学院院士 金展鹏

金展鹏,男,1938年11月出生,广西荔浦人,中共党员,中南大学材料科学与工程学院教授,博士生导师。他早年投身于材料科学,20世纪70年代开始进行相图热力学和相变动力学的研究。他发展了结构特点不同的相的热力学模型和相图优化计算方法,构筑了一系列金属合金、氧化锆基陶瓷及人     

肉豆蔻酸-十四醇二元复合相变材料的相变特性研究

以肉豆蔻酸(MA)和十四醇(TD)为原料,采用熔融共混法制备了MA-TD二元复合相变材料,利用步冷曲线法测定不同质量比的MA-TD复合相变材料的结晶温度,绘制相图获得二元体系低共晶点,确定了MA-TD共晶混合物的质量比为36∶64,其结晶温度为32.7℃。差示扫描量热测试结果表明MA-TD共晶混合物的相变潜热为227.08kJ/kg。傅里叶变换红外光谱测试表明,复合相变材料中MA和TD的分子结构未发生变化,两者为物理复合。经过500次0～60℃冷热循环,MA-TD二元复合相变材料的相变温度基本不变,说明该复合相变材料的热稳定性较好。     

Ti-AlN界面组分分布的二次离子质谱研究

采用电子束蒸发方法在200℃的抛光AlN陶瓷衬底上淀积厚度为22nm的Ti膜，并在高真空中退火。利用二次离子质谱（SIMS）对样品进行了深度剖析，给出了Ti／AlN界面组分分布随退火温度和时间的变化关系。在界面区发现了铝化物及其他反应产物。结合卢瑟福背散射谱（RBS），X射线衍射分析（XRD）和Ti-Al－N三元相图推断，铝化物是Ti-Al二元和Ti-Al-N三元化合物。经850℃退火4h后其主要由Ti2AlN组成。     

计算热力学及其在材料科学中的应用(英文)

简要综述了材料科学领域中计算热力学与动力学的模型、数据库、软件及应用。介绍了当前最常用的软件。详细解释了用于描述不同相热力学性质的重要模型,以及获取热力学数据库中模型参数的优化过程。此外,还阐述了平衡计算中最常用的一种算法。最后本文给出了一些使用软件和数据库计算相平衡和相图,以及结合动力学数据用于相变及其过程模拟的示例。     

Ti-Si-C三元系组元化学位稳定性相图

收集并计算了Ti-SI-C三元系在1200度温度下各组元化合物的热力学数据,利用Ti-SI-C三元系在该温度下的平衡相图以及对碳化物未知热力学数据所做的估算,计算该三元系中各组元化学位并作出的相应的化学位稳定性相图。     

Cu-Zn 合金马氏体相变热力学

假定 Cu-Zn 合金马氏体相变中新、旧原子存在 Bain 机制所示的对应关系,则沿用已知的热力学数据,以 BWG 模型处理 Cu-Zn 合金的有序问题,推导出相变驱动力ΔG~(β′→α′)的普遍表达式。以该式计算了Cu-Zn 合金马氏体相变的平衡温度 T(?)及马氏体相变点 M_s,其中 M_s 与实验结果很好吻合。计算证明,母相有序化是 Cu-Zn 合金发生热弹性马氏体相变的必要条件,有序度对 M_s 有显著的影响。     

Experimental investigation and thermodynamic calculation of Bi–Ga–Sb phase diagram

Abstract

Phase diagram of the Bi–Ga–Sb ternary system has been investigated by DTA and SEM with EDS measurements. Phase transition temperatures in four vertical sections and isothermal section at 500°C were studied. Experimental results were compared with calculated phase diagram by the Calphad method.     

Maple在相图计算中的新应用

本文简要介绍了相图的计算原理和过程以及Maple软件的特点。以二元相图为例，用Maple软件进行了Cu-Ag二元系合金的相图计算，计算结果与实验结果吻合良好，进一步展示了Maple软件在相图计算中应用的可能性。     

Phase transformations in the ternary Ag–Ga–Sb system

Phase diagram of the Ag–Ga–Sb ternary system was extrapolated using calculation of phase diagrams (CALPHAD) method. Phase transition temperatures of the alloys with compositions along three vertical sections with constant molar ratios Ga/Sb = 1, Ag/Ga = 1 and Ag/Sb = 1 were measured using differential scanning calorimetry (DSC). Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) was used for identification of phases in equilibrated samples. Experimental results were compared with thermodynamic prediction.     

Experimental investigation and thermodynamic calculation of phase equilibria in the In–Sb–Zn ternary system

Binary thermodynamic data, successfully used for phase diagram calculations of binary systems In–Sb, In–Zn, and Sb–Zn, were used for prediction of phase equilibria in ternary In–Sb–Zn system. The liquidus projection, invariant equilibria and several vertical sections were calculated using the CALPHAD method. Alloys, situated along three calculated vertical sections, were investigated by differential thermal analysis (DTA). The experimentally determined phase transition temperatures were compared with predicted results. Phase identification of selected samples was done using scanning electron microscopy (SEM) with energy dispersive X-ray microanalysis (EDS).     

Phase equilibria and crystal structure of ternary compounds in Al-rich corner of Al-Er-Y system at 673 and 873 K

Phase equilibria in the Al-rich corner of the Al-Er-Y ternary system from 65 at.% to 100 at.% Al at 673 and873 K were investigated,and the two isothermal sections were established by X-ray diffraction(XRD),scanning electron microscope(SEM) and electron probe micro analysis(EPMA).Three ternary-phase regions are observed and the phase relations are similar at both isothermal sections.There are two ternary compounds,and a complete crystal structures and composition ranges of the two ternary compounds are determined as τ₁(Al_75-76Er_15-22Y_2-10,R-3 m) and τ₂(Al_75-76Er_11-17Y_7-14,P6₃/mmc) via XRD,focused ion beam coupled with transmission electron microscope(FIB-TEM) and EPMA.Meanwhile,the solubilities of the third element in the binary compounds at both temperatures are measured.The solubility of Er inβ-Al₃ Y phase reaches to 6.6 at.% and that of Y in Al₃ Er phase reaches to 1.5 at.% after annealing at 873 K.The temperature effect is not obvious for the phase equilibria at 673 and 873 K,but it increases the solubility of Er in β-Al₃ Y,while it is not obvious for both the solubility of Y in Al₃ Er and that of Er and Y in(Al).The phase equilibria of the Al-Er-Y ternary system determined by the present work have provided new phase diagram data for a future thermodynamic assessment of this system.     

Thermodynamic Assessment and Experimental Investigation of Fe-Al-C System

Phase diagram information of the Fe-C, Fe-Al and Al-C systems are reviewed and the Fe-Al-C system is assessed. A FeAlC database is created by combining a set of thermodynamic parameters established by Kumar and SSOL database in Thermo-Calc software package. Ternary phase diagrams are calculated with FeAIC and the newly developed Thermo-Calc databases SSOL2 and SSOL4. The FeAIC database is the best one to describe the Fe-Al-C system. Al and A3 values on the vertical section containing 1.5 wt pct AI are calculated with the FeAIC database in this work. To validate the thermodynamic calculation, critical temperatures Ac1 and Ac3 are determined by using dilatometer analysis. There exist some errors between the calculated values and the experimental results. So further optimization of the Fe-Al-C system regarding bcc and fcc phases is necessary. The experimental data in this work could be of some value in further optimization.     

Magnetic Quantum Rotors

A new quantum system, magnetic quantum rotors, is presented. A magnetic rotor—a rotor possessing nonzero spin—is exemplified by the oxygen molecule. Of the exchange, spin-orbital, and spin-figure interactions contributed by the spin degree of freedoms only the latter was taken into consideration in this study. Phase diagrams of magnetic quantum linear rotors in a crystal field are studied for a system where all angular momentum states are allowed (all-J system) and for one where angular momentum is restricted to have odd values (odd-J system). It is found that depending on the crystal field and the value of the spin-figure coupling constant the orientational phase transition line can display a set of critical points (one, two, three or none in the case of the all-J systems and one, two or no critical points in the case of the odd-J systems) which are responsible for the topology of the phase diagram.     

Tracking multi-phase boundaries using an integration-based approach

An integration-based method to track multi-phase boundaries for multi-component alloys systems is proposed. The foundation of the method is considering the phase boundary tracking as an initial value problem. It starts with the utilization of Gibbs–Duhem relation to find the slope of a phase boundary (the partial derivatives of the solvus temperature with respect to the equilibrium phase composition) and the partial derivatives of partition coefficients with respect to the equilibrium phase composition. Then, with these derivatives and a pair of known initial points on a phase boundary, the rest of the phase boundary can be calculated using a numerical integration technique such as the Runge–Kutta or Predictor–Corrector method in a stepwise manner. The integration method has been applied to track various types of phase boundaries in binary, ternary and quaternary systems. The calculated ones are in good agreement with the ones obtained by the commercial CALPHAD software Thermo-Calc. It provides a different computational method for the tracking of multi-phase boundaries and might be useful in the calculation of phase diagram when combined with the overlapping of Zero Phase Fraction (ZPF) lines technique and global minimization technique.     

The Calculation of Phase Equilibrium Between Structural Phases with a Magnetic Transition by the Cluster Variation Method

The phase equilibrium between structural phases with a magnetic transition is investigated using the CV-pair approximation of the cluster variation method (CVM). By the geometric analysis of the grand potential, it is demonstrated that the grand potential and effective chemical potential of the different structural phases with a magnetic transition can be separated into paramagnetic and magnetic terms. In addition, the molar grand potential-effective chemical potential curve can be obtained from the relevant molar energy diagram. A calculation method for the phase equilibrium between structural phases with a magnetic transition is proposed; this method is applied to the / phase equilibrium in the Fe–Mn binary system, and the calculated phase diagram closely approximates the experimental diagram.     

1,3,4-Oxadiazole epoxy resin-based liquid crystalline thermosets and their cure kinetics

Liquid crystalline thermosets were synthesized based on a difunctional liquid–crystal (LC) epoxy resin monomer, namely 2,5-bis(4-glycidyloxyphenyl)-1,3,4-oxadiazole with various tetrafunctional crosslinkers such as diaminodiphenyl methane, diaminodiphenyl sulfone, and diaminodiphenyl ether. The epoxy monomer was characterized by infrared and nuclear magnetic resonance spectroscopy. Cure kinetics of a stoichiometric mixture of epoxy monomer and diaminodiphenyl methane was investigated by differential scanning calorimetry (DSC) for specimens cured under various cure conditions. The nematic LC texture for the cured specimen was identified by polarized microscopy and confirmed by X-ray diffractometry. Phase diagram of cure time versus transition temperature was constructed based on the DSC data for epoxy/DDM system. The diagram displayed the changes of melting transition, isotropic transition, and glass transition temperatures as curing proceeds.