基于氧在固态铜中进行非稳态扩散的动力学研究

在内氧化动力学实验的基础上,研究了铝质量分数为0.19%、0.42%、0.72%和0.94%的铜铝合金平板形试样在1023 K、1123 K、1223 K和1273 K温度下的内氧化动力学,并采用定量金相技术测量了内氧化层的深度,推导了平板形状铜铝合金试样的内氧化动力学方程.经内氧化实验检验证明,该方程可以较精确的描述平板形状铜铝合金的内氧化动力学.基于该方程和内氧化深度测试,计算出了氧在铜中的渗透率.     

Parabolic growth of oxide solid solutions on binary alloys

The growth of oxide solid solutions on binary alloys has been described using the ternary diffusion model put forward by Wagner and subsequently modified by Dalvi and Coates and Bastow, Whittle, and Wood. A more refined defect model where the presence of all types of vacancy species within the scales is considered has been adapted to obtain the diffusivities of cations in the scales as a function of oxygen potential and cation composition. In addition, correlation effects on cation jump frequencies have been included to account for additional compositional dependence of the diffusivities. Results have been analyzed for oxidation of Ni-Co to (Ni, Co)O at 1273°K in 1 atm oxygen. Improved agreement between calculated and experimental cation concentration profiles indicates that this approach is better than to arbitrarily assign functional forms to the compositional and oxygen activity dependencies of the diffusivities, and demonstrates that an accurate as possible model for the point defect structure of the oxide is required for correct interpretation of the growth of these solid solution types of scales.Deceased July 23, 1982.     

The parabolic growth of oxide solid solutions on binary alloys: A semiempirical approach

The growth of solid solution oxide scales on alloys has been described by considering either the transport of the cations themselves, or that of the defect species in the oxide lattice. The two approaches have been shown to be similar. However, it has become apparent that the simplified defect model implicitly assumed in previous analyses using the ionic transport approach is not adequate to fully describe the variation of ionic diffusivities with oxygen potential or oxide composition. Further analyses, using a combination of the two approaches, are suggested.     

铜中氧对铜/钢扩散复合界面的影响

用扫描电镜、能谱分析和电子探针等方法研究了不同含氧量的铜/钢双金属棒扩散复合界面氧化物的形成及影响因素.结果表明：当铜中氧含量较少时,扩散复合中基本不形成氧化物.当铜中含氧量较高时,界面附近铜中形成弥散分布的氧化物颗粒;随扩散温度的升高和时间的延长,氧化物颗粒尺寸变大,分布区域变宽;界面剪切断裂时裂纹在氧化物处形成、扩展.从扫描电镜和电子探针结果中可以确定在铜/钢界面附近的氧化物为Fe2O3并从热力学角度分析了氧化物的形成原因.     

Transient liquid phase diffusion bonding of copper alloy to stainless steel using CuMn alloys as interlayer

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Influence of diffusion bonding conditions on bonding strength of damping copper alloy to stainless steel

The experimental investigation of different tran sition metals was carried out in the diffusion bonding joints of Cu alloys (CuAlBe) to stainless stee l (1Cr18Ni9Ti). The microstructure of the joint was analyzed with microscopic examination, SEM, EPMA and X-ray diffraction. Following conclusions have been draw n: (1) The joint strength with the Ni interlayer was higher than that with Cu in terlayer when the welding parameters were same;(2)When Ni interlayer was thinner ,Al could interact with Ni and Fe,and the intermetallic compounds,such as Fe3A letc,were formed in the interface,which decreased the strength of the joints;(3 ) When the bonding temperature was higher,because of the diffusion of Cu in Ni being faster than Ni in Cu,a Kirkendall effect was produced,which also decreased the strength of the joints.     

Ti/Al固相扩散反应行为表征及动力学研究

本研究在Ti和Al均过量时,表征了Ti/Al在520℃~630℃范围内不同时间下的固相扩散反应行为。结果发现,当试样退火46小时后,Ti/Al界面的反应产物为单一相TiAl3,而且TiAl3/Al界面上的TiAl3生长速度比Ti/TiAl3界面上的TiAl3生长速度快。此外,本研究建立了TiAl3生长动力学模型,Ti/Al扩散反应激活能为170.1 kJ/mol,动力学指数为n=0.5,TiAl3生长随时间呈抛物线规律增长,利用Ti/Al复合粉末体作为试验材料,证明了所建立的TiAl3生长动力学方程的正确性。     

Phase relations in the Fe-Cr-O system at 1200°C investigated by means of a diffusion couple technique

The morphology and composition of diffusion layers formed in multiphase ternary diffusion couples of Cr or Cr-Fe alloy vs. FeO or FeCr₂O₄ have been studied by electron probe microanalysis, X-ray diffraction, and microscopy. A new technique for annealing of the couples has been developed. Phase relations at 1200° C of the ternary system Fe-Cr-O are discussed, and diffusion paths of the investigated couples are plotted on the isothermal section of the ternary phase diagram.     

激电效应的非线性扩散方程及其形式解

矿物的激发极化效应， 总是与发生在矿物／ 溶液界面上的各种电极过程紧密相关的。从岩矿石激电效应的电化学机理出发， 通过研究矿物／ 溶液界面离子的运动规律， 写出了描述离子浓度的暂态变化和空间变化的有关偏微分方程。根据界面双电层结构理论以及对方程组稳态解的分析， 导出了描述激电效应的非线性扩散方程。由于方程的非线性及复杂的边界条件， 作者采用了本征表象中的扰动展开方法，近似处理了该数学问题， 得到了方程的形式解， 并提出了将电化学理论与非线性理论相结合的一种新的激电理论。     

A review of the role of short-circuit diffusion in the oxidation of nickel,chromium, and nickel-chromium alloys

The evidence for short-circuit diffusion during the oxidation of nickel, chromium, and nickel-chromium alloys is reviewed. On the basis of experimental evidence for the Ni/NiO and Cr/Cr₂O₃ systems, inferences are made about the role of short-circuit diffusion through the oxide scales forming on the binary nickel-chromium alloys. The review highlights the importance of scale microstructure in governing oxidation rates.     

Transition from internal to external oxidation for binary alloys in the presence of an outer scale

The critical concentration required for the transition from internal to external oxidation of the most reactive component B of a binary A-B alloy for the case of simultaneous formation of an outer AO scale is calculated by extending Wagner's original analysis, which excluded the presence of an AO oxide. It is shown that the formation of an outer AO scale tends to produce an increase in the critical concentration of B, essentially as a result of a decrease of the enrichment of B in the internal oxidized region. Examples of the calculation of some parameters are presented to examine the effect of the different factors on the properties of internal oxidation and on its transition to the formation of an external scale of the oxide of the less noble component.     

Development of preferential intergranular oxides in nickel-aluminum alloys at high temperatures

The development of intergranular oxides in dilute Ni-Al alloys containing 0.55–4.10% Al in Ni-NiO packs and in 1 atm oxygen at 800–1100°C has been examined. In the Ni-NiO packs, preferential intergranular oxide penetration as well as internal oxidation occurs in every case, except in the higher aluminum-containing alloys at 1100°C. Several different types of intergranular oxide morphology were observed, depending on alloy aluminum concentration and on temperature. The oxides in the more dilute alloys are thin and relatively continuous and are accompanied by preferential penetration of internal oxide particles in the adjacent grains. Thicker intergranular oxides are precipitated in the more concentrated alloys while, in some situations, numerous fine oxide particles are formed well ahead of the main intergranular oxide. The intergranular oxidation is facilitated by high stress development in the specimens due to increases in volume as internal and intergranular oxides are formed. These stresses create microvoids in the grain boundaries immediately ahead of the advancing internal and intergranular oxides, resulting in preferential nucleation and growth of further intergranular oxides. This is the case particularly at the lower temperatures where other stress-relief processes cannot operate. The resulting relatively continuous, incoherent intergranular oxide-metal interface allows a high flux of oxygen to the advancing intergranular oxide front. Preferential intergranular oxidation is much less extensive in the presence of a thickening external NiO scale, due to accommodation of the volume increases on internal oxide formation by vacancies injected into the alloy from the growing cationdeficient scale.British Nuclear Fuels, Windscale Works, Seascale, Cumbria, U.K.     

Influence of external mechanical loadings (creep,fatigue) on oxygen diffusion during nickel oxidation

This study deals with the influence of various mechanical loadings (fatigue, creep, creep-fatigue) on oxygen diffusion in a particular system, oxidizing nickel. A distinction between the behavior of the oxide layer and underlying nickel was noted during the first step of oxidation at 550°C, in P_{O 2}=1 atm. Mechanical loading causes a decrease of the oxygen mobility through the oxide scale (factor of 10³). The oxide thicknesses on nickel undergoing mechanical loadings are different than for an unloaded sample, due to distinct contributions of the oxygen and nickel fluxes in the growing oxide. In the substrate, the ingress of oxygen becomes easier with a constant tensile load (creep). The intergranular-oxygen diffusion coefficient, D_i, is increased by a factor of 10² with respect to other samples. In creep, oxygen diffusion takes place along grain boundaries of a structure with smaller grains than in unstrained Ni. A short fatigue period during creep-fatigue decreases the sensitivity of nickel to intergranular-oxygen diffusion.     

Analysis of oxygen-18 tracer profiles in two-stage oxidation experiments (I): predominant oxygen diffusion in the growing scale

Typical two-stage oxidation experiments in high-temperature oxidation studies on metals are analyzed. Two cases of predominant oxygen diffusion in the scale are studied: pure volume diffusion and simultaneous transport via grain boundaries and via the bulk. An analytical expression for the growth of the oxide layer is given for the assumption that the chemical potential of the oxygen varies linearly over the oxide layer. The numerical treatment of the differential equation is improved so that the calculation is possibly faster and/ or more accurate compared to a method given in the literature. The experimental profiles are described by four parameters, the grain boundary width, the grain radius, and the volume and grain boundary diffusivities. Two equations correlating these parameters can be extracted from the profiles. Two benchmark tests are described for testing the program. An analytical solution is presented which approximately describes the distribution of O-18 in the oxide layer for pure volume diffusion. Experimental SIMS profiles on Fe-Cr-Al alloys are explored on the basis of our calculation.     

Investigation of the process of diffusion bonding of alloys based on titanium nickelide

The results of investigations of diffusion bonding of an alloy based on titanium nickelide are presented. The effect of the welding conditions on the strength of the joint in sheet semi-finished products is investigated. The experimental results show that the main reason for the reduction in the mechanical properties of the welded joint is the interaction of the weld surfaces with residual oxygen. This results in the formation of brittle intermetallic compounds enriched with titanium at the periphery of the weld zone.     

基于容量参数的二次电池嵌入型电极材料固相扩散系数的测定方法

介绍了一种以容量参数为主变量的测定锂二次电池中电极材料固相扩散系数的方法.该方法只需颗粒半径这一辅助参数,通过球型扩散模型建立了恒流-恒压充电容量(RPG)比,进一步发展成为容量间歇滴定技术(CITT).采用RPG法可在较宽的电压范围内测定嵌入型电极材料的平均固相扩散系数,实验结果重现性好.由RPG法测得0～1.5 V时锂离子在石墨电极中的平均固相扩散系数值为1.055×10-10cm2/s.由CITT技术测得锂离子在LiMn2 O4中的固相扩散系数在3.95 V和4.12 V左右存在个两个极小峰,且随着循环次数的增加,扩散系数值逐渐增大.     

Influence of prior internal oxidation on the oxidation of dilute Co-Cr alloys in oxygen

The influence of an initial preinternal oxidation treatment in Co/CoO on the subsequent oxidation behavior of a series of dilute Co-Cr alloys (containing 0–1.5 wt. % Cr) in 10⁵ and 10³ Pa oxygen at 1473–1623 Khas been investigated. Particular emphasis has been placed on determining the solubility and mobility of Cr³⁺ ions in CoO. Use has been made of subsequent annealing in argon .     

Enhanced Oxygen Diffusion Along Internal Oxide–Metal Matrix Interfaces in Ni–Al Alloys During Internal Oxidation

A study of the internal oxidation of dilute Ni–Al alloys in an NiO/Ni Rhines pack was performed at 800, 1000, and 1100°C. Considerable deviations from the classical internal oxidation model have been observed. The rate of internal oxidation depends not only on the concentration of the alloying element but also on its nature, which contributes to determining the size, shape, orientation and distribution of the internal oxide precipitates. For instance, the precipitates in the Ni–Al alloys are continuous rods, arranged in a cone-shaped configuration that extends from the surface to the internal oxide front. The observed depths of internal oxidation for the various concentrations of aluminum are discussed and related to the morphologies of the internal oxide precipitates. The apparent N^(s) _oD_o values determined from internal oxide penetrations increase with increasing solute content in the alloy. It is postulated that diffusivity of oxygen is enhanced along the internal oxide–metal matrix interface compared with that in the metal matrix.     

The oxidation of Ni-70 wt.%Cr in oxygen between 1073 and 1473°K

Oxidation of the relatively simple, two-phase alloy Ni-70 wt.%Cr in oxygen between 1073 and 1473°K results in the formation of a Cr₂O₃ scale containing less than O.5 wt.% Ni in solid solution. The oxidation kinetics are irreproducible for an initial period, which is brief at 1073 and 1273°K but much more pronounced at 1473°K, both in duration and degree. This behavior is associated with the failure of the protective Cr₂O₃ scale. However, after longer periods a compact layer of Cr₂O₃ becomes established under isothermal conditions and results in a change to more reproducible kinetics, especially at 1073 and 1273°K. Oxidation causes chromium depletion and the formation of a single-phase zone which separates the scale and the two-phase bulk alloy. The depth of Cr₂O₃ internal oxide coincides with this zone. The oxidation behavior is compared with that of more Ni-rich, single-phase Ni-Cr alloys, with particular reference to the effects of the constitution of the underlying alloy and the integrity of the protective oxide.