有色金属合金体系气液相平衡研究进展

真空蒸馏是从液相到气相的传质过程,合金的气液相平衡相图是真空蒸馏设计的重要理论依据,根据气液相平衡相图可以预判蒸馏最终产物以及分离提纯效果,因此准确的气液相平衡相图对于真空蒸馏生产实践以及废弃二次资源回收分离提纯具有重要的实际意义。本文首先介绍了合金体系的分离系数,然后介绍了气液相平衡成分图的计算方法,并指出了其不足,接着介绍了气液平衡相图的计算方法,同时给出了理论计算与实验值存在偏差的原因。     

700℃热浸镀锌三元等温截面测定

通过制作两个固-液扩散偶,并通过实验探索700℃下Fe-Zn-Sn系中不同成分制备平衡合金的方法,利用SEM-EDS等手段测定Fe-Zn-Sn三元系700℃等温截面部分相关系。实验结果显示:这部分相图是由L、α(Fe)、Γ三个单相区,L+α(Fe)、Fe Sn+Fe_3Sn_2、Γ+Fe_3Sn_2、L+FeSn、L+Γ、α(Fe)+Γ六个两相区,α(Fe)+L+Γ、α(Fe)+L+Γ、L+Fe Sn+Fe_3Sn_2三个三相区组成的;锡含量在一定范围内,锡含量的增加导致镀层厚度减少。     

三元体系LaCl_3-HCl-H_2O 298.15 K下相平衡的研究

采用等温溶解平衡法测定了三元体系LaCl_3-HCl-H_2O 298.15 K下的溶解度数据,分别采用质量滴定法和重量法对平衡后的液固相组成进行了测定,得出在298.15 K下随着体系中盐酸浓度的增加,LaCl_3浓度在减小,平衡后析出的固相均是LaCl_3·7H_2O_((s)),且用两种方法测定的相平衡数据较一致,说明这两种方法对该体系相图的测定较准确。     

Ag-Cu-Sn-Cu_3P相图及该系钎料强韧机理初探

采用DTA，WDX和金相分析等方法研究测定了5％Sn－Ag－Cu－CU3P四元相图Cu角的部分变温截面；给出了该四元系五相平衡反应及各平衡相的成分；分析了该系钎料的强韧化机理．     

Rb2SO4-C2H5OH-H2O三元体系的溶解度研究

采用半微量相平衡实验装置，研究了Rb2SO4-C2H5OH-H2O三元体系0-60℃的等温平衡溶解度，发现该体系在实验研究温度范围内饱和溶液相都是不分层的乙醇-水溶液。用TPD软件（三角相图绘图软件）绘制了相应的平衡相图，“Schreinmakers”湿渣结线法确定平衡固相皆为无水Rb2SO4；同时给出了体系10-60℃的等温溶解度方程及30℃时C2H5OH对Rb2SO4的盐析率曲线。     

FexO-TiO2体系的固相反应机理

采用扩散偶法研究了1323~1473 K下FexO-Ti O2体系的固相反应,反应过程中氧分压由一定比例的CO-CO2混合气体控制.扩散偶截面的微观形貌用电子探针进行观察,并对Fe2+、Ti4+和O2-离子的扩散浓度轮廓进行定量分析.结合Fe O-Ti O2体系相图确定了固相反应中有钛铁晶石、钛铁矿和假铁板钛矿相生成,且它们的生长受扩散控制.依据扩散组元的摩尔分数变化绘制了铁离子的扩散路径图,并在此基础上描述了该体系的固相反应机理.     

空气气氛条件下CaO-Al2O3-CeO2渣系在1500℃的相平衡关系

采用热力学平衡实验,结合SEM-EDS等检测方法,确定了空气气氛条件下CaO-Al₂O₃-CeO₂渣系在1 500℃的相平衡关系,并绘制出该渣系的等温相图.在空气气氛条件下,CaO-Al₂O₃-CeO₂渣系在1 500℃时存在着三种三相平衡(CA+CA₂+CeO₂,L+CaO+CeO₂,L+CA+CeO₂)和两种两相平衡(L+CeO₂,L+CaO),根据各平衡相关系划分了相应相区,且CeO₂在该渣系中的最大溶解度为28%(质量分数).     

集团变分法(CVM)及其在合金相图计算中的应用

介绍了集团变分法的集团概率变量、配置熵等统计分析的理论基础及Helmholtz自由能的描述模型.提出了巨势及相对化学势的几何分析理论.讨论了应用集团变分法和巨势分析理论进行相平衡计算的过程,并分析了同结构平衡相图计算的若干实例.     

三元体系PEG 4000-Cs2SO4-H2O在25,35和45 ℃时的相平衡研究

采用自制的相平衡研究装置，测定了PEG 4000-Cs2SO4-H2O三元体系在25，35和45℃时的等温平衡溶解度，同时给出了该体系的完整相图，在相图中观察到6个相区。结果表明，该体系双液相区随着温度的升高略有增加，结线的斜率也随温度的升高而增大。用四参数方程y=a bx^0.5 cχ dχ^2对该体系的双液线进行了拟合，拟合结果较好。用Othmer-Tobias方程和Bancroft方程对该体系结线的实验数据进行了关联，所有线性相关系数均大于0．98。热重分析确定平衡固相组成为无水硫酸铯。     

相图在SiO_2—Al_2O_3系耐火材料中的应用

相图是用以表示相平衡以及相变化的几何图形,也可以认为它是研究相平衡及其变化的工具。相平衡则表示一物系固——固、固——液和液——液之间在各种温度下共存以及彼此间相互消长的情况。简言之,相平衡表示了相组成及其数量随温度的变化关系,因而相图能够对生产实际     

Al-Zn(Cu)合金的相变和Al-Zn-Cu系相图

Al-Zn-Cusystemistheimportantbasisfor practicalAlalloysandZnalloys[1].Amiscibility gapofthefccphaseexistsabove277℃inthe Al Znsystem[2].Thealloywhosecompositionis atthetopofthemiscibilitygapiscalledsym metricalalloyAlZn.Thisalloyhasmanytypical properties.Theimportantoneisthatthespi nodaldecompositioneasilytakesplaceinit.In ordertoavoidthedecomposition,Cuhasbeen added,whichiseffective.Additionof2%Cu molefractioncoulddelaythespinodaldecompo sitionfortwogrades[3,4].AlZn 2Cuisanalloy which…     

Application of computational thermodynamics to Fe/Ni,Fe-3%Si/Ni and 316L/Ni systems produced by powder metallurgy

The commercial simulation software packages, Thermo-Calc and DICTRA, are widely used to predict phase formation and diffusion in materials prepared by traditional metallurgical processes. The goal of this work was to clarify whether the software can also be applied to materials produced by powder metallurgy techniques. For this purpose, diffusion couples of the material combinations Fe/Ni, Fe-3%Si/Ni and 316L/Ni were prepared by two techniques: co-pressing of powders followed by co-sintering and joining of two sintered parts followed by annealing. Thermo-Calc and DICTRA were used to predict interface formation and phase transformations during heat treatments. Scanning electron micrography and energy-dispersive X-ray spectrometry showed the formation of interdiffusion interfaces. The diffusion rate was higher in co-sintered couples, resulting in broader interdiffusion zones than those predicted by simulations, but the annealed couples exhibited interdiffusion profiles similar to those predicted by DICTRA simulations. In general, simulations and experimental results showed the same tendencies.     

The effect of continuous heating on the phase transformations in zinc- iron electrodeposited coatings

The crystal structure and phase transformations of electrodeposited zinc-iron coatings were investigated by several techniques. The phase composition of as-plated zinc-iron coatings was found to contain both 17 phase and8 phase and, according to the equilibrium phase diagram, was in a nonequilibrium condition for the compositions investigated. The transformation toward equilibrium during heating was a two-stage process. The first stage of transformation, at temperatures between 25 °C and 360 °C, is accomplished with very little change in composition, and the phase transformation occurs within the coating itself. It is proposed, through a simplified analysis, that the phase transformation in this stage is supported by short-range diffusion. In the second stage of the transformation, at temperatures above 360 °C, the iron content in the coating increases as a result of interdiffusion between the coating and the base steel, and the phase structure moves to the iron-rich side in accordance with the equilibrium phase diagram. MINGYUAN GU, formerly Visiting Research Scientist, Energy Research Center     

Reaction diffusion in the NiCrAl and CoCrAl systems

The oxidation life of a physically vapor-deposited overlay protective coating based on the Ni-Cr-Al or Co-Cr-Al (M-Cr-Al) systems is controlled by aluminum consumption resulting from alumina spalling, erosion, and interdiffusion with the substrate. The rates of these processes are determined by coating and substrate composition, service environment, and temperature. The purposes of this study were 1) to determine the effect of coating and substrate chemistry on the kinetics of interdiffusion and their relation to diffusion-zone constitution and 2) to develop a procedure for analyzing diffusion in multicomponent, multiphase systems. Semi-infinite diffusion couples with MCrAl sources representative of coatings and sinks representative of nickel-or cobalt-base gas turbine alloys were annealed at 1000, 1095, 1150, or 1205°C for as long as 500 h. The couples were examined by optical microscopy and layer growth measurements were made. Parabolic growth constants can be correlated with source aluminum content for a specific sink composition since changes in source aluminum content are more important than changes in chromium content. Sink composition is as important as source composition in determining β-recession kinetics in diffusion couples and life in finite coatings. Nickel-base alloys are more stable sources and stronger sinks than cobalt-base alloys. Total and diffusion activation energies were determined from layer growth constants. By introducing the concept of β source strength which can be determined from the appropriate phase diagrams, the Wagner solution for consumption of a second phase in a semiinfinite couple was successfully applied to the analysis of the MCrAl couples. This provided a method 1) for correlating β-recession rate constants with couple composition, 2) for determining reliable total and diffusional activation energies, and 3) for calculating interdiffusion coefficients.     

镁的合金化与合金相图

论文分析了镁基合金二元和多元相图的研究现状；指出了镁合金在合金化中存在的问题。在此基础上探讨了在镁合金的设计与研究过程中如何进行相图的研究。指出由6－10个元素组成镁合金集团进行合金相图的实验测定和热力学计算的方案是可行的。     

A graphical method for constructing coherent phase diagrams

The equilibrium conditions for a stressed two-phase coherent solid are employed to develop a graphical construction for coherent equilibrium. We show that in certain cases when the stress is generated by a misfit between the precipitate and matrix, the equilibrium coherent phase compositions can be found drawing parallel tangents to the molar free energy curves of the phases measured in the absence of stress. Total energy diagrams and phase stability diagrams can be constructed to determine the combinations of phase compositions and volume fractions which yield unstable, metastable, and stable states. Through these constructions it is possible to show that elastic stress can result in the appearance of cusps on a total energy plot, indicating the presence of an nonanalytic total free energy of the system as a function of alloy composition. Finally, we show how a stable and metastable coherent phase diagram can be determined qualitatively using these constructions.     

Diffusion in the nickel-rich part of the Ni−Al system at 1000° to 1300°C; Ni3Al layer growth,diffusion coefficients,and interface concentrations

The formation of the Ni₃Al layer in NiAl (55 at. pct Ni)-pure Ni diffusion couples at temperatures above 1000°C has been found to be controlled almost completely by volume diffusion. At 1000°C and below, the relatively small grain size of the Ni₃Al compound in the layers caused such a large contribution from grain boundary diffusion, that the layer growth rates at 1000°C exceeded those at 1100°C and even those at 1200°C. In Ni₃Al (75at. pct Ni)-pure Ni diffusion couples the Ni₃Al compound rapidly converted into the solid solution of aluminum in nickel. Volume-diffusion coefficients calculated by the Boltzmann-Matano method yielded heats of activation of 55, 64, and 65 kcal·mol^?1 for NiAl, Ni₃Al and the solid solution of aluminum in nickel, respectively. In addition, eleven different types of diffusion couples were prepared from various Ni?Al alloys and annealed at 1000°C. Marker interface displacements and observations of porosity in these couples yielded a more detailed picture of the Kirkendall-effect than earlier work had done. The ratio of the intrinsic diffusion coefficients at the marker interface,D _NI/D _Al, is greater than one in the nickel-rich NiAl phase. For the Ni₃Al phase no statement can be made on the basis of this work. When the marker interface is located in the nickel solid solution,D _Ni/D _Al is smaller than one. The phase boundary concentrations in these couples did not show the expected deviation from the equilibrium concentrations in two-phase alloys; this finding is discussed with regard to the free-energycomposition diagram.     

Application of the diffusion couple to study phase equilibria in the Fe-Cr-S ternary system at 600 °C

The sulfidation of Fe-Cr alloys has a large financial significance for industries that use fossil fuels, such as the electric utility industry. Therefore, the sulfidation of a series of Fe-Cr alloys was studied at 600 °C using a solid-state diffusion couple technique. The diffusion couple technique combined Fe_0.95S powder and FeCr binary alloys together in a configuration that allowed for post-heat-treatment microanalysis using an electron probe microanalyzer (EPMA). The results showed that only two different diffusion couple microstructures formed in samples spanning the entire Fe-Cr binary range. The Fe-rich alloy diffusion couples contained a surface αFeCr layer and an internal sulfide precipitate layer that contained three different sulfide phases. The Cr-rich alloy diffusion couples also possessed an internal precipitate layer, as well as a thick, triplex interfacial scale. The ternary elemental diffusion was described using diffusion paths plotted on the 600 °C isothermal section of the Fe-Cr-S phase diagram. The results also showed that samples with less than 51 wt Pct Cr were more sulfidation resistant. The accuracy of the existing Fe-Cr-S 600 °C isothermal section was assessed, and it was determined that the τ phase field had a larger composition than previously published.     

Experimental Investigation of the Ce-Mg-Mn Isothermal Section at 723 K (450 °C) via Diffusion Couples Technique

The isothermal section of the Ce-Mg-Mn phase diagram at 723 K (450 °C) was established experimentally by means of diffusion couples and key alloys. The phase relationships in the complete composition range were determined based on six solid–solid diffusion couples and twelve annealed key alloys. No ternary compounds were found in the Ce-Mg-Mn system at 723 K (450 °C). X-ray diffraction and energy-dispersive X-ray spectroscopy spot analyses were used for phase identification. EDS line-scans, across the diffusion layers, were performed to determine the binary and ternary homogeneity ranges. Mn was observed in the diffusion couples and key alloys microstructures as either a solute element in the Ce-Mg compounds or as a pure element, because it has no tendency to form intermetallic compounds with either Ce or Mg. The fast at. interdiffusion of Ce and Mg produces several binary compounds (Ce _x Mg _y ) during the diffusion process. Thus, the diffusion layers formed in the ternary diffusion couples were similar to those in the Ce-Mg binary diffusion couples, except that the ternary diffusion couples contain layers of Ce-Mg compounds that dissolve certain amount of Mn. Also, the ternary diffusion couples showed layers containing islands of pure Mn distributed in most diffusion zones. As a result, the phase boundary lines were pointing toward Mn-rich corner, which supports the tendency of Mn to be in equilibrium with all the phases in the system.     

铁矿烧结过程中的活化技术研究

添加活化剂是降低烧结能耗的有效措施。通过对烧结物理机制的探讨，得出了铁矿烧结活化技术开发中需要遵循的三条基本判据，即溶解度判据、偏析判据和扩散判据。经过分析得出扩散判据为其根本判据。还借助相图原理探讨了活化剂的筛选原则，并提出了逐级局部活化法。