Cu-Al合金内氧化的热力学分析——Ⅱ热力学函数的应用

这是(Cu-Al合金内氧化的热力学分析》一文的第Ⅱ部分。对Cu-Al合金内氧化的热力学条件进行了分析，绘制了内氧化的热力学条件区位图。结果表明：区位图中择优氧化区位很大，范围由上、下限氧分压确定，其中：lgPo2max=(-17611／T) 12．91，lgPo2min=(-55830／T)-(4／3)lg[％Al] 19．95，但实际的内氧化区位是靠近上限Po2的一个很小区域；溶度积Ksp和残余Al浓度都是极小量，内氧化可进行得很彻底；内氧化控制中温度和氧分压的调节必须同步：理想的内氧化工艺条件应是：采用1223K左右的高温，介质中的氧分压力求接近或等于上限Po2;为了避免氧化，降温过程宜采用通H2急冷的方法。     

Cu-Al预合金粉末中Al内氧化工艺的分析

对高能球磨制备的Cu-Al预合金粉末中Al内氧化的工艺进行了研究．结果表明，温度是决定临界氧分压Po2的关键因素，随着温度的升高，临界氧分压增加．适当提高温度可以减小环境氧分压的控制难度．高能球磨制粉对Al内氧化的热力学条件影响不显著，但对动力学条件影响显著．当Al的质量分数大于0．5％时，对于不同的Al含量的Cu-Al预合金粉末应有不同的加热工艺．当工艺参数适宜时，采用Cu-Al预合金粉末可以制备出组织均匀的Al2O3／Cu复合材料，其中Al2O3颗粒粒径2—5μm，颗粒间距5—10μm．     

内氧化法制备Al2O3/Cu复合材料的研究现状

综述了内氧化法制备Al2O3／Cu复合材料的研究现状，总结了内氧化法制备Al2O3／Cu复合材料的必备条件，对内氧化动力学和热力学进行了详细的阐述，并以Cu2O为氧源，采用内氧化法制备了Al2O3／Cu复合材料，验证了其优越的室温和高温性能；对以复合材料棒材为原料制备的点焊电极进行装机试验，结果表明其寿命为传统Cu-Cr—Zr电极的3～5倍；最后着重分析了内氧化法制备Al2O3／Cu复合材料发展过程中亟待解决的问题。     

内氧化法制备Al2O3/Cu复合材料的载流摩擦磨损特性

采用内氧化法制备了Al2O3／Cu复合材料，研究了复合材料在载流条件下的摩擦磨损特性，并进行了微观组织结构分析。结果表明：采用内氧化法制备的Al2O3／Cu复合材料，在铜基体中弥散分布着纳米级的Al2O3颗粒；载流条件下，该复合材料的抗摩擦磨损性能显著优于铬青铜合金；电流较小时具有磨粒磨损和粘着磨损的共同特征，电流较大时以粘着磨损为主。在试验范围内，电流比载荷对磨损率的影响显著。     

Ag-Cu合金内氧化研究

针对Ag-Cu合金内氧化动力学和内氧化后的组织进行研究。结果表明:内氧化后,在氧化温度和氧分压一定时,氧化层深度与氧化时间呈抛物线关系;在氧分压和氧化时间一定时,氧化层深度与氧化温度呈指数关系;在氧化时间和氧化温度一定时,氧化层深度lgE与lgPO2为线性关系。氧化温度不同时,Ag-Cu合金内氧化层组织不同;在相同氧化工艺条件下,内氧化层深度随溶质Cu含量的增加而减小。     

Cu—Al合金内氧化工艺及动力的研究

对 Cu- Al合金的内氧化工艺及其动力学进行了系统研究。结果表明 :本实验条件下以 12 2 3K,0 .5 h内氧化工艺所得材料的性能最佳 ,其显微组织特征是 Cu基体上均匀弥散分布着纳米级 γ- Al2 O3粒子。理想条件的内氧化初期和实际条件下的内氧化动力学曲线服从抛物线规律。温度、时间、Cu- Al合金粉颗粒半径和 Al浓度是实际内氧化控制的 4要素 ,它们间的函数关系近似满足下式 :t=6 .79R2 CBexp(2 32 5 1/T)。实际内氧化时间不宜过长 ,内氧化温度应该 :112 3K相似文献   

基于热力学计算的水工况对耐热钢高温氧化行为影响

基于热力学计算方法,对6种不同的水工况条件下的高温氧分压进行了计算和对比.计算结果显示,TP347H和T91两种材料在570℃时高温氧化产物类型转变的临界氧分压约为1.0×10-15,而常规的加氧工况OT(1)、纯水工况、还原性全挥发处理工况AVT(R1)在此条件下的氧分压均高于1.0×10-10,因此认为常规的加氧工...     

高温钛铝基合金及其氧化行为

作为高温材料，人们利用铝化物、硅化物或者钦化物当成基体或者涂层，因为在它们上面能够形成保护性的氧化皮，后者分别是稳定的氧化物─Al2O3、SiO2和BeO．据知，这些氧化物鳞次在高温氧化条件下是最有防护作用的．研究表明，为了在高温条件下提供全月间化合物基体上的连续防护层，其表面氧化友必须满足以下四项基本要求：第一，热力学稳定性；第二，缓慢的增厚速度（低生长速度）；第三，对基体的良好粘附性；第四，容易形成和再形成．令人感兴趣的对一川二元系金属间化合物有四种，它们是Ti3Al(a2)、TiAl（r）、TiAl2和TiAl3．另外…     

内氧化法制备Al2O3/Cu点焊电极的装机试验

采用内氧化法制备了0．6Al2O3／Cu复合材料，以该复合材料棒材为原料制备了点焊电极，并进行了装机试验和微观组织结构分析。研究结果表明：采用内氧化法制备的0．6Al2O3／Cu复合材料在铜基体中弥散分布着纳米级细小Al2O3颗粒。由于Al2O3颗粒硬度高，热稳定性和化学稳定性好，使该复合材料制备的点焊电极抗塑性变形能力强、抗坑蚀能力优良、再结晶温度高，并具有优越的抗粘接能力，使用寿命是铬锆铜电极的3倍多。     

激光熔覆合成TiCp／Al过程反应热焓的确定和计算

为深入研究激光熔覆反应合成TiCp／Al复合材料过程，数值计算该过程的温度场和流场时需将所发生的化学反应热纳入计算。因此本文采用在试样扫描过程中突然停止激光发射的办法，得到反应过程中不同阶段所形成的组织，进而判断出各阶段所发生的反应；利用差热分析法(DTA)和热力学计算法确定反应热焓值。研究表明：激光熔覆条件下Al-Ti-C粉料层中合成反应的过程为：先发生3Al Ti→Al3Ti反应，再发生Al3Ti C→TiC Al反应。3Al Ti→Al3Ti的反应热为146．63kJ／mol，Al3Ti C→TiC Al的反应热为38．60kJ／mol。该反应热焓值可用于温度场和流场的数值模拟计算。     

The influence of an intermediate annealing treatment on the oxidation of copper and nickel

A study has been made of the effects of an intermediate, isothermal annealing treatment in argon on the oxidation kinetics of copper and nickel in 1 atm oxygen at 800 and 1100°C, respectively, using a semiautomatic microbalance. Changes in scale morphology and composition have been investigated using various physical techniques. The outer CuO layer formed on copper during oxidation dissociates very rapidly on annealing to give CU₂O and oxygen since the partial pressure of oxygen in the gas is below the dissociation pressure of CuO but above that of Cu₂O at 800°C. The CuO layer is quickly re-formed on reoxidation in oxygen. There are relatively few other changes in the oxide morphologies of either metal during annealing, although the small grains present in the scale adjacent to the metal after oxidation are able to grow. During reoxidation both metals show a reduction in oxidation rate constant because of the decrease in total cation vacancy concentration in the scale and the reduced cation vacancy gradient across the scale brought about by the reduction in oxygen partial pressure at the oxide-gas interface during annealing. The reoxidation rate constants following annealing approach those recorded prior to annealing as the equilibrium cation vacancy levels in the scales are reestablished in the oxidizing environment. Rosenberg's method for analysis of the kinetics of reoxidation has enabled the equilibrium concentrations and diffusion coefficients of cation vacancies in CU₂O and NiO during oxidation in 1 atm oxygen at the appropriate temperatures to be estimated approximately. These show reasonable agreement with literature values.     

Internal oxidation thermodynamics and microstructures of Ag-Y alloy

The thermodynamic data of pure Ag and Y were calculated. The phase constitution, composition of micro-region and microstructures of Ag-Y alloy after internal oxidation were investigated by X-ray diffractometry(XRD), energy dispersion spectrometry(EDS) and scanning electron microscopy(SEM). The results show that the internal oxidation behavior of Ag-Y alloy is feasible from the view of thermodynamics. The upper limit of oxygen partial pressure of Ag-Y alloy oxidation is a function of temperature. Two phases (Ag and Y2O3) appear in Ag-Y alloy after the internal oxidation. The surface of Ag-Y alloy is convex because of the volume expansion of oxide in the alloy and the composition of the convex part is Ag. In Ag-Y2O3 sintered bulk Y2O3 particles are distributed inhomogeneously and conglomerated seriously, but they are dispersed uniformly in the Ag matrix after severe plastic deformation.     

Internal Oxidation of Fe–Mn–Cr Steels,Simulations and Experiments

A multi-element and multi-phase internal oxidation model that couples thermodynamics with kinetics is developed to predict the internal oxidation behaviour of Fe–Mn–Cr steels as a function of annealing time and oxygen partial pressure. To validate the simulation results, selected Fe–Mn–Cr steels were annealed at 950 °C for 1–16 h in a gas mixture of Ar with 5 vol% H₂ and dew points of ? 30, ? 10 and 10 °C. The measured kinetics of internal oxidation as well as the concentration depth profiles of internal oxides in the annealed Fe–Mn–Cr steels are in agreement with the predictions. Internal MnO and MnCr₂O₄ are formed during annealing, and both two oxides have a relatively low solubility product. Local thermodynamic equilibrium is established in the internal oxidation zone of Fe–Mn–Cr steels during annealing and the internal oxidation kinetics are solely controlled by diffusion of oxygen. The internal oxidation of Fe–Mn–Cr steels follows the parabolic rate law. The parabolic rate constant increases with annealing dew point, but decreases with the concentration of the alloying elements.     

微细浸染型金矿酸性热压氧化预处理动力学研究

以氧气消耗速率表征氧化速率,研究了微细浸染型硫化物金矿热压氧化预处理过程动力学的影响因素,考察了矿浆pH值、温度、矿样粒度、氧分压、气液界面面积和矿浆浓度对氧化速率的影响,以及氧化率和氧化速率的关系。结果表明,矿浆pH2.5时,保持较高的氧化速率;氧化速率随温度升高、氧分压增加和矿浆浓度降低而增大;增加气液接触面积可提高氧化速率,当矿浆浓度为33%、氧分压1.6 MPa,在优化条件下,气液接触比表面积达到25 m2/m3,40 min可完成氧化预处理。     

渗碳或碳氮共渗时内氧化的热力学分析

应用热力学原理,在渗碳或碳氮共渗处理时给出了钢中合金元素Cr、Mn、Ti发生内氧化的热力学判据。计算了实际炉内气氛中氧分压的值,结果表明在实际处理时钢中Cr、Mn、Ti元素在热力学上均会发生内氧化,讨论了碳势及氧电势对内氧化的影响,分析了内氧化的氧化特征,浅了内氧化的动力学。     

The kinetics and mechanism of molten copper oxidation by top blowing of oxygen

The rate of liquid copper oxidation plays an important role in the separation of impurities from copper during fire refining. However, the importance of factors affecting the rate of oxygen uptake by liquid copper is not clear. Top blowing oxidation of molten copper shows that the rate of oxidation is almost independent of the average oxygen concentration of the copper and proportional to the oxygen flow rate of the gas mixtures used. A pressure monitoring technique was used to determine the effect of a carrier gas such as N₂, helium, and CO₂, and the effect of the lance distance from the liquid surface on the partial pressure of oxygen in the gas phase. A numerical model was developed to help understand the mechanism of oxygen mass transfer into the molten copper. For more information, contact T. Marin, University of Toronto, Department of Materials Science and Engineering, 184 College St., Toronto, Canada M5S 3E4; e-mail tanai.marin@utoronto.ca.     

Zum Mechanismus der Hochtemperatur-Oxidation von Kupfer-Aluminiumlegierungen

Mechanism of high temperature oxidation of copper aluminium alloys The oxidation (950 °C, oxygen pressure 10^?2 to 760 Torr ) follows a linear kinetic law after the first 3 to 5 min. Low oxygen concentrations produce preferential internal oxidation with Al₂O₃ being precipitated in statistical distribution in the copper matrix or — with higher a/Al contents — forming a barrier layer near the surface. This layer would slow down diffusion of copper ions; this effect would be even more pronounced at high oxygen pressures, where couprous oxide is present. The rate constant of the oxidation is drastically reduced by higher Al contents (> ～ 1%).