Au-Ni合金中组元的平均原子体积和偏摩尔体积的关系

在系统合金科学框架中建立有关无序合金的平均摩尔性质（体积和势能）的函数。通过对这些函数进行推导,可以得到平均摩尔体积函数、偏摩尔体积函数及派生出与成分相关的函数。在组元的偏摩尔性质和平均摩尔性质之间的普适方程、差分方程、在偏摩尔性质和平均摩尔性质之间不同参数的约束方程和普适的Gibbs-Duhem公式。可以证明从合金平均摩尔性质的不同函数计算的偏摩尔性质是相等的,但总体来说偏摩尔性质不等于给定组元的平均摩尔性质,即偏摩尔性质不能代表相应组元的摩尔性质。通过计算Au-Ni系中组元的偏摩尔体积和平均原子体积以及合金的平均原子体积,证明所建立的公式和函数的正确性。     

Correlation between lattice distortion and friction stress in Ni-based equiatomic alloys

Many recent efforts have been made to apply traditional theories for solid solution strengthening to explain the strength increase in concentrated equiatomic alloys (or high-entropy alloys), but always faced the challenge of differentiating solvent from solute atoms. In this report, we conducted a systematical analysis of Ni-based equiatomic alloys with a face-centered cubic structure and found that the lattice distortion in this alloy system could be simply described by the parameter of atomic size mismatch. It was found that lattice friction stresses of these alloys were well correlated with the lattice distortion. Dislocation core width in this Ni-based alloy system was also estimated and compared with that in the pure nickel. The intrinsically high strength in high-entropy alloys was probably resulted from a high lattice friction stress.     

Densities and molar volumes of solid lithium-magnesium (Li-Mg) alloys

Densities of solid Mg and Li-Mg alloys were measured for five compositions of mole fractions of Li equal to 0.05,0.1,0.15,0.20, and 0.25, respectively, by the dilatometric method. The curvilinear dependence of the density on temperature (room temperature up to 873 K) was observed for all investigated alloys. Results could be described by parabolic equations. The molar volumes of Li-Mg alloys were calculated from the density measurements. It has been found that the densities of solid Li-Mg alloys show positive deviations from linearity, and the molar volumes exhibit negative deviations from linear dependence for all samples in the experimental concentration range. It was possible to describe the dependence of density on temperature and concentration by a polynomial. Coefficients of thermal expansion were calculated and discussed. The density of the (Li) phase along the (Li)/[(Mg) + (Li)] boundary was calculated and described by a temperature-dependent polynomial of the third power.     

Microstructure evolution of nanoprecipitates in half-Heusler TiNiSn alloys

The microstructures of thermoelectric TiNiSn half-Heusler alloys have been studied in detail. For concentration ratios that are slightly rich in Ni, a high density of Heusler-phase nanosized precipitates tended to precipitate within a half-Heusler matrix. The morphology and average size of the Heusler nanoprecipitates were very sensitive to the Ni concentration ratio in the half-Heusler matrix of the alloys. Smaller Heusler nanoprecipitates with coherent ellipsoidal (<5 nm) and disc (<10 nm wide) morphologies tended to precipitate within the matrices of alloys with slightly elevated Ni concentration ratios (Ti:Ni:Sn = 1.0:1.1:1.0). However, much larger coherent discs (<45 nm wide and <5 nm thick), semicoherent platelets (up to 1 μm long and <30 nm thick) and spheres (up to 1 μm wide) were observed in the matrices of the alloys with larger Ni concentration ratios (Ti:Ni:Sn = 1.0:1.2:1.0). Tetragonal structures were observed in the coherent Heusler nanoprecipitates. The formation of such structures was closely associated with the size, morphology and interface coherency of the nanoprecipitates. Moreover, most of the coherent Heusler nanoprecipitates were preferentially oriented parallel to the cubic {0 0 1}_HH orientations. Interfacial defects between the Heusler and half-Heusler phases, as well as lattice point defects, Ni antisites and vacancies, were found to be closely related to the formation of the Heusler nanoprecipitates. A mechanism has been proposed in this study to describe the coarsening of the Heusler nanoprecipitates via the formation of lattice point defects and interfacial defects.     

Processing,microstructure, and properties of β titanium alloys modified with boron

The development of next-generation βTi alloys is expected to involve very attractive combinations of strength-toughness-fatigue resistance at large cross sections, improved and affordable thermomechanical processing, and enhanced elevated temperature capability. This article describes the development of βTi alloys that are modified with small boron (B) additions to achieve these goals. Two important aerospace alloys, Ti-15Mo-2.6Nb-3Al-0.2Si and Ti-5Al-5V-5Mo-3Cr microalloyed (0.1%) with B were considered. Ingots that were 70 mm in diameter and 500 mm in length were cast using induction skull melting. A detailed microstructural characterization and tensile property evaluation were conducted. Microalloying with B refines the cast grain size to about 50 μm, which enhances strength and ductility. The effect of B additions on the microstructural stability and properties in the as-cast condition was established. The implications of B additions on the microstructural evolution and affordability of subsequent processing is also discussed. This paper was presented at the Beta Titanium Alloys of the 00’s Symposium sponsored by the Titanium Committee of TMS, held during the 2005 TMS Annual Meeting & Exhibition, February 13–16, 2005 in San Francisco, CA.     

硼对亚共晶Al—Si合金的细化作用

利用ＤＳＣ,ＳＥＭ 和Ｘ 射线衍射等手段, 分析了硼对纯铝及亚共晶ＡｌＳｉ 合金的细化作用。发现在纯铝中, ＡｌＢ２ 分布在铝的晶界上, 无细化作用; 而在ＡｌＳｉ 合金中, ＡｌＢ２ 具有细化α（Ａｌ） 晶粒的性能。分析认为, 在ＡｌＳｉ 加硼的熔体中, ＡｌＢ２ 虽不能作α（Ａｌ） 的核心, 但它为Ｓｉ 的析出提供形核衬底,随温度的下降, α（Ａｌ） 在Ｓｉ 相上形核, 达到细化的目的。     

Grain refinement of cast titanium alloys via trace boron addition

The grain size of as-cast Ti–6Al–4V is reduced by about an order of magnitude from 1700 to 200 μm with an addition of 0.1 wt.% boron. A much weaker dependence of reduction in grain size is obtained for boron additions from >0.1% to 1.0%. Similar trends were observed in boron-modified as-cast Ti–6Al–2Sn–4Zr–2Mo–0.1Si.     

Influence of epitaxial stress on spinodal decomposition in binary alloys with large size effects: application to the Au–Ni system

Within the framework of Cahn’s pioneering theory of spinodal decomposition, the effect of the epitaxial stress on the stability of a binary alloy solid solution against infinitesimal compositional fluctuations is revisited. It is shown that the elastic energy term due to a coherent lattice mismatch with a substrate modifies the linearised diffusion equation. This term is particularly high when size effects between the two constituents are strong. It is then necessary to take into account anharmonic terms in the expression of the elastic energy. From the modified diffusion equation, a new spinodal curve, called the epitaxial coherent spinodal, may be calculated for different substrate lattice parameters. The results of the model are compared with recent experiments on coherently grown (001) Au–Ni alloys. A modulated structure has been evidenced upon annealing which is in good agreement with our calculations.

Résumé

Dans le cadre de la théorie de la décomposition spinodale développèe par Cahn, nous présentons l’effet des contraintes épitaxiales sur la stabilitéd’une solution solide d’alliage binaire soumise ádes fluctuations de compostion infinitésimales. Les contraintes induites par l’épitaxie cohérente sur un substrat ayant un paramètre de maille différent de celui de la solution solide considérée sont àl’origine d’un terme d’énergie élastique dont il faut tenir compte dans l’équation de diffusion. Ce terme devient particulièrement important lorsque les effets de taille entre les deux constituants sont grands. Nous montrons qu’il est alors nécessaire de considérer dans l’expression de l’énergie élastique les termes anharmoniques. Une nouvelle spinodale, appelée spinodale cohérente épitaxiale, peut être calculée pour différentes valeurs du paramètre de maille du substrat. Les calculs sont comparés avec les résulats expérimentaux obtenus sur des alliages Au–Ni (001) élaborés de manière cohérente. Une structure modulée a étémise en evidence au cours de recuits, ce qui est en accord avec les résultats du modèle.     

Electrodeposition of platinum metal and platinum-rhodium alloy on titanium substrates

A method for application of an adherent platinum (Pt) and platinum-rhodium (Pt-Rh) alloy plate to a titanium (Ti) substrate includes steps of surface pretreatment, anodization, and electrodeposition of Pt and Pt-Rh alloy from their electrolytic baths consisting of H₂Pt₂Cl₆·6H₂O (20 gL⁻¹), and HCl (300 gL⁻¹) for a Pt bath. The Pt-Rh bath consists of H₂Pt₂Cl₆·6H₂O (20 gL⁻¹), and HCl (300 gL⁻¹) and Rh₂ (SO₄)₃ (2 gL⁻¹). At the optimum conditions of electroplating, the Pt and Pt-Rh deposits were formed over the anodized Ti substrates with high adhesion, brightness, and high current efficiency (35.33% for Pt and 70.38% for the Pt-Rh alloy).     

Some comments on the misfit and coherency loss of Al3Sc particles in Al–Sc alloys

An attempt of refining a recently reported calculation of the temperature dependent misfit between Al and Al₃Sc particles is given. Further, the impact of a temperature dependent misfit on the calculated diameter for coherency loss of Al₃Sc precipitates is demonstrated. The origin of misfit dislocations is also briefly discussed.     

Ultrasonic detection of ductile-to-brittle transitions in free-cutting aluminum alloys

Resonant ultrasound spectroscopy (RUS) is applied to detect the ductile-to-brittle and brittle-to-ductile transitions in an AA6262 free-cutting aluminum alloy during thermal cycling. It is shown that the RUS method is sensitive enough to detect reliably the melting and solidification temperatures of micro-sized Mg₃Bi₂–Bi eutectic particles responsible for these transitions, although the volume fraction of the particles is very small (~1%) and is even decreasing with the cycling. The proposed RUS approach is compared with differential scanning calorimetry (DSC); the latter method is shown to be unable to detect the transition temperatures especially when transition intervals are broad. The results reveal that the phase transitions of the eutectic particles exhibit a significant hysteresis and pronounced asymmetry between melting and solidification.     

B元素对Fe-Cr-C系耐磨堆焊合金组织和耐磨性的影响

采用直径为1.6 mm的细径药芯焊丝,利用CO₂气体保护焊堆焊的方法制备了含有1.0%~3.0%C(质量分数),15%~20%Cr,0%~2.0%B的高铬堆焊合金.研究了B₄C含量对堆焊合金的硬度及耐磨性的影响.结果表明,堆焊合金的硬度从57.1 HRC增加到65.2 HRC,硬度提高14.2%;堆焊层合金的相对耐磨性从3.5倍提高到18.0倍.借助光学显微镜、扫描电镜和X射线衍射等微观分析方法,研究了堆焊合金的显微组织及碳化物分布形貌.结果表明,堆焊合金的显微组织主要由铁素体+奥氏体+(Fe,Cr)₇C₃组成,加入B₄C可显著改善堆焊合金层基体组织,使碳化物(Fe,Cr)₇C₃数量增加且呈弥散分布.     

High-temperature sulfide corrosion of cobalt-chromium alloys

The kinetics and mechanism of high-temperature sulfidation of cobaltchromium alloys were investigated. It has been found that the sulfidation rate of low-chromium alloys, up to 2% Cr, is higher than that of pure cobalt. The one-layer homogeneous scale on these alloys is a solid solution of chromium sulfide in cobaltous sulfide. In the case of alloys containing more chromium, up to 43%, sulfidation rate decreases gradually with chromium content, the scale consisting of two layers. The growth mechanism of scales as well as the influence of chromium concentration on sulfidation rate is discussed.This work was carried out under contract No. 03.10 coordinated by the Institute of Physical Chemistry, Polish Academy of Sciences.     

Advances in brazing of creep-resisting alloys

The problems of brazing of creep-resisting nickel and intermetallic alloys based on titanium aluminide are investigated. Advantages of using adhesion-active brazing alloys based on Ni–Cr–Zr, Pb–Ni–(X), Ti–Zr–Fe, and Ti–Zr–Mg systems for brazing are described.     

BCC结构Nb-Mo合金系的特征原子序列及无序合金的性质(英文)

根据系统合金科学的思想,结合实验晶格常数和生成热,综合考虑合金能量、体积、原子状态之间的相互关系,确定BCC结构Nb-Mo合金系的相互作用方程为第9方程;同时,确定Nb-Mo合金系中Nb和Mo特征原子序列和特征晶体序列的基本信息;根据无序合金的特征原子浓度计算了无序Nb(1-x)Mox合金的电子结构和物理性质,其物理性质的变化趋势与电子结构的变化极其一致。     

The limiting molar partial enthalpies of mixing of iron, cobalt, nickel, palladium and platinum in liquid gallium and indium

Gallium and indium have been used as solvents for the determination of the molar partial enthalpy of mixing Δ_mixh_m^o(TM, Ga or In) (denoting liquid transition metal (TM) in infinite liquid gallium or indium) of the pure liquid transition metals Fe, Co, Ni, Pd and Pt by direct reaction calorimetry between 1000 K and 1500 K with the exception of Δ_mixh_m^o(Fe, In) (because of the shape of its equilibrium phase diagram). All the limiting enthalpies listed below refer to the liquid state. With pure gallium as solvent, they correspond to the reaction

TM(liq) − nGa(liq) → TM₁Ga_n(liq)

at the experimental temperature T_e, with n 1.

1. (i) Δ_mixh_m^o in gallium is found for Fe, Co, Ni, Pd and Pt to be −2, −44, −82, −144 and −155 kJ mol⁻¹.

2. (ii) Δ_mixh_m^o in indium is found for Co, Ni, Pd and Pt to be +28, −25, −127 and −114 kJ mol⁻¹.

In both solvents, these limiting enthalpies vary with a similar trend. This observation makes it possible to predict the limiting molar partial enthalpy Δ_mixh_m^o(Fe, In) of mixing of iron in indium as +70 kJ mol⁻¹. The results have been compared with the data proposed by Miedema and co-workers.     

Oxidation of Ni-base alloys in atmospheres with widely varying oxygen partial pressures

The oxidation behavior of the Ni-base alloys IN 617, IN 713 LC, Ni20Cr, and Ni20Cr+Si has been investigated in the temperature range from 850°C to 1000°C in air and at low-oxygen partial pressure p(O₂) (10^–19 to 10^–16 bar). With the exception of alloy IN 713 LC, the materials show no influence of p(O₂) on the oxidation mechanisms and the kinetics. This result can be explained by the formation of a dense Cr₂O₃ layer, the growth rate of which is controlled by the Cr ion interstitial concentration in Cr₂O₃ at the phase boundary oxide/alloy and the mobility of Cr ions in Cr₂O₃. For the alloy IN 713 LC which develops a dense Al₂O₃ layer in air, a modified transition mechanism at low p(O₂) leads to the formation of Cr₂O₃ at the surface and a strong internal oxidation of Al.     

饰品用贵金属合金及其钎焊工艺的发展

概述了金、银两类贵金属及其钎焊工艺的发展。介绍了各类型饰品用金、银合金种类、特性和应用范围,并针对不同类型的金、银合金所适用的钎焊材料及钎焊工艺。首饰用贵金属合金所使用的钎料种类繁多,国家标准中已规定适用于各行业的银合金钎料(包括含钯钎料)48个牌号,金合金钎料19个牌号,但未进一步对饰品用贵金属钎料进行规定。近年来市场对饰品用贵金属合金的需求逐年增长,对其成分的安全无害标准亦有提升,故饰品用贵金属合金钎料的无害化、系列化和标准化已成为必然趋势,相关研究在制定行业标准、提高国际市场竞争力上具有重要意义。     

Corrosion of iron-, nickel-, and cobalt-base alloys in atmospheres containing carbon and oxygen

The corrosion of iron-, nickel-, and cobalt-base alloys has been studied in atmospheres containing carbon and oxygen in the temperature range 894–1366 K. It was observed that preformed Cr₂O₃ films are not effective barriers to carbon transport in atmospheres in which the oxide is not stable but that stable, growing Cr₂O₃ films are excellent barriers to carbon penetration. The presence of Fe-containing oxides on Fe-Ni-Cr and Fe-Cr alloys cause the scales to be permeable to carbon. This phenomenon was found to be sensitive to alloy surface preparation. Carbon transport through oxide scales may occur by two mechanisms: diffusion or molecular transport through physical defects. The present work has evidence of the latter but cannot rule out the former in cases where the carbon activity is sufficiently large. In gases containing CO and CO₂ in which Cr carbide is stable Cr₂O₃ was found to form at the carbide-alloy interface by oxygen transport through the carbide. In A-CH₄ Fe-Ni-Cr were found to undergo graphitization attack. The results were consistent with the formation and subsequent decomposition of metastable carbides, as proposed by Hochmann.