Note on a Convenient Method of Electropolishing Aluminium Alloys

The general problem of electrodeposition of metallic coatings on to active metal substrates is briefly discussed. A detailed study of the electrodeposition of copper from a bath containing copper acetate dissolved in acetic acid-pyridine solutions containing 20% by volume of pyridine is then presented. The variation of cathode current efficiency as a function of current density and temperature was studied at current densities in the range 1 to 12 A/ft² at temperatures from 25° to 62·5°C. At 6 A/ft², temperature had the most marked influence on current efficiency which increased from ~ 60% at 25° to a maximum value of 112% at 50°C. A wide variety of types of coating were obtained from the bath by appropriate variation of the deposition conditions. These varied from ductile, matt, adherent coatings, with columnar structures resembling those from acid copper baths, to ductile, high reflecting coatings with layered structures which were similar to those obtained from aqueous baths in the presence of addition agents. The results of the investigations are discussed with respect to present knowledge concerning the chemistry of the acetic acid-pyridine system.     

Thermal Resistance of Low-Alloyed Chromium Alloys

The oxidation kinetics of low-alloyed -2 and 1-17 chromium alloys is investigated at a temperature from 1273 to 1673 K for 1000 h. It is shown that even at a temperature from 1473 to 1673 K the heat resistance of these alloys is higher than that of the 648 nickel-containing alloy at a temperature from 1273 to 1373 K. This allows to recommend the alloys as heat-resistant materials operating at a temperature up to 1573 K.     

The Electrodeposition of Cobalt–Chromium Alloys from Sulfate–Oxalate Solutions

The kinetics of separate and concurrent discharge of cobalt and chromium ions from sulfate–oxalate solutions is studied. Cobalt–chromium alloys with the cobalt content of 4 to 94% and carbon content of 1 to 4% are obtained. At a concurrent discharge of chromium and cobalt ions, the deposition potential of chromium is shifted by 150 to 200 mV in the positive direction. The shift depends on the current density and cannot be accounted for by the energy of mixing of the components. The alloying of chromium with cobalt decreases the overpotential of the hydrogen discharge. The codeposition with chromium did not decelerate the reduction of cobalt ions in contrast to the electrodeposition of nickel. The main reasons for the difference between the effect the alloying with chromium produces on the electrochemical reduction of nickel and cobalt, which are similar in their properties, are considered.     

镁及镁合金的高纯净化

对各种杂质在镁及不同系列的镁合金的行为及对镁合金性能的影响作了系统的分析。论文指出镁合金高纯净 化是镁合金扩大应用范围的关键之一,而镁及镁合金高纯净化是一项十分艰巨的任务。国内外已研究成功的镁合金高纯 净化工业技术同今天镁合金的发展需要还有差距,开发新的镁合金高纯净化技术是今后的重大任务。     

Influence of Chromium Carbides on the High Temperature Oxidation Behavior and on Chromium Diffusion in Nickel-Base Alloys

Two simple cast nickel alloys Ni–30Cr–0.2C and Ni–30Cr–0.8C were oxidized at 1,000, 1,100 and 1,200°C. Their behaviors were characterized using thermogravimetry techniques and their parabolic and chromia volatilization constants were determined by analyzing the versus −m curves. The constants obtained were generally in good agreement with experimental mass-gain kinetics and chromium-balance aspects. A higher carbon content i.e., a higher carbides density leads to higher values of the transient linear-oxidation constant K _l , of the parabolic constant K _p , and obviously also of the volatilization constant K _v . Chromium diffusion coefficients through the zone affected by oxidation were calculated from the oxidation kinetics and chromium gradients. They increase when the carbide density increases.     

The Electrodeposition of Zinc on Aluminium and Its Alloys

Dull nickel deposits may be given a brilliant finish by a brief anodic treatment in a sulphuric acid solution; polishing action is obtained over a wide range of conditions. The method has possibilities as an alternative to bright nickel plating and the process has been investigated from this point of view. Under suitable conditions, the process does not adversely affect the protective properties of the deposit and the quality of the finish is at least as good as that obtained by bright nickel plating. The method also enables designs to be formed on nickel surfaces by localising the area polished, and attractive finishes may be produced in this way.     

超弹性合金及应用

超弹性合金与形状记忆合金相同也是马氏体相变型合金 ,只不过前者是由应力产生马氏体相变 ,这种应力感生的马氏体相变所形成的材料特性就是超弹性。所谓超弹性就是材料在外力作用下产生远大于其弹性极限的应变量 ,当去掉载荷时它又能自动恢复其变形的现象。典型的超弹性合金有二种 :①富Ni的Ni Ti二元系合金 ,添加小于 1%的第 3元素 ,其应力感生的马氏体为单斜晶 ;②Ni Ti Cu X合金 ,其马氏体相为斜方晶 ,显示小应力滞后。超弹性合金应用十分广泛 ,最早大量生产使用的是女性ブラジャ -のアンダ -ワイヤ (乳罩底丝 ) ,目前多用于眼镜架 ,…     

锶在镁及其合金中的作用

在镁合金中添加适量的Sr,不仅可以降低过冷度,且易吸附在固/液界面的前沿形成富Sr的吸附膜,降低晶粒生长速度,从而细化晶粒.细小的晶粒有利于提高镁合金液的补缩能力,减少显微缩松,增加铸件的致密度.Sr与H2反应生成SrH2,减少氢气孔的析出.此外,在Mg-Al合金中加入Sr可以生成一些高温稳定的新相(Al10Mg13Sr),明显改善镁合金的高温蠕变性能和抗热裂性能.     

The Electropolishing of Nickel in Urea-Ammonium Chloride Melts

Nickel may be electropolished in melts based on urea containing 5–20% w/w of ammonium chloride and 0–3·5% w/w of anhydrous nickel chloride, held at 120–135°C. The optimum applied potential difference across a cell with a vertical anode spaced 1 cm. from the cathode is 2·5–3 v., and the optimum current density is 0·15—0·4 amp./cm.². Considerably higher current densities also give polishing but lead to much gas evolution and increase the tendency to pitting; still higher current densities produce a grey film on the metal surface. The melts age with time, so that the optimum current density falls, and become useless after about three days at temperature; they are partially restored by the addition of fresh urea.

There is an induction period before polishing begins (shorter the higher the current density) during which the metal dissolves normally; the onset of polishing is determined by a rise of anode potential (1·5–1·8 v.) similar to that found in anodic passivation. The evidence suggests that the rise is due, as in passivation, to the formation on the anode surface of a compact film, which during the polishing process, however, dissolves at its outer surface as fast as it is formed. It is suggested that this mechanism is general in electro-polishing, and it is shown that it can account for the avoidance of etching characteristic of the process.     

铬对Fe-P-C系非晶晶化过程的影响

用热分析法测定了Fe-P-C-Cr系几种非晶合金的DTA曲线，通过这些曲线的变化可看出不同铬含量对晶化温度及晶化过程的影响。此外，还做了晶化前后各样品的穆斯堡尔谱分析，从而获得晶化过程及晶化相的相关信息。     

铬含量对Fe-Cr-B堆焊合金显微组织及耐磨性的影响

目的在Fe-x Cr-3.5B-0.1C药芯焊丝中加入不同含量的铬,了解铬含量对堆焊合金硼化物形貌以及耐磨性能的影响。方法采用CO_2气体保护堆焊的方法在Q235钢基板上制备Fe-Cr-B系耐磨合金,利用光学显微镜、XRD、SEM等方法观察堆焊合金层的显微组织结构,以及湿砂橡胶轮磨粒磨损试验机对堆焊层进行磨粒磨损试验。结果堆焊合金层主要由铁素体枝晶、马氏体、珠光体和硼化物组成,硼化物随着Cr含量的增加发生Fe_2B到M_2B(M=Fe,Cr)的转变,它主要分布在金属基体的连续网状和鱼骨状结构中。凝固过程中,当Cr质量分数大于9%时,首先形成初生M_2B颗粒,随后形成共晶的M_2B和BCC结构的Fe基固溶体,这种共晶的微观结构主要由基体和长条状的M_2B硼化物组成。从Cr与(Fe,Cr)的原子数分数比值可以看出,硼化物发生从Fe_2B→(Fe,Cr)_2B→(Cr,Fe)_2B的转变。铬含量对Fe-Cr-B系耐磨堆焊合金的组织、硼化物形貌有较大影响。由于硼化物空间结构的变化,硼化物的显微硬度会随着铬原子进入Fe_2B而逐渐提高。结论随Cr含量的增加,及共晶硼化物硬质相的析出,堆焊合金的硬度和耐磨性呈现持续提高的趋势。当Cr含量为20%时,合金中生成的长条状M_2B相作为耐磨骨架无序的分布且镶嵌于基体中,合金耐磨料的磨损性能比Cr含量为9%时的提高了约7.4倍。     

原子吸收光谱法测定贵金属合金中的铬

采用原子吸收光谱法测定Co Cr Pt Si O2、Au Ni Cr、Ni Pd Cr BSi、Ni Cr B合金中铬含量,研究了影响铬测定的因素及其消除条件。结果表明,用盐酸-硝酸、氢氟酸密闭消解样品,高氯酸发烟驱除剩余氢氟酸,氯化铵或水合肼消除大量镍(II)、硅(IV)或金(III)的影响,用亚硫酸钠转化可将铬(VI)完全转化为高灵敏度的铬(III);标准曲线线性范围0~6.00μg/m L,检出限0.004μg/m L;测定含量为5%~7%的铬,相对标准偏差0.82%~1.29%,加标回收率为93.34%~110.80%。     

Electropolishing parameters of NiTi alloy

Electropolishing has been used in NiTi alloy in several fields for its special characteristics, but its essential details and electropolishing mechanism have not been reported yet as a demand from business competition, which, to a great degree, restricts the application and extension of the electropolishing technology. The effect of processing parameters on nitinol electropolishing was explored. Besides the electrolyte, other factors that influence the electropolishing are temperature, current density, time, spacing between anode and cathode, electrolyte stirring, etc. Studies on the effect of the temperature on the electropolishing process show that the higher the temperature is, the bigger the electropolishing rate is, following the near Gauss law. The relationship between the temperature and the surface roughness follows a near parabolic law, and the relationship between the temperature and the surface reflectivity follows a near sigmoidal law. The relationship between the electropolishing voltage and the current density follows a near cubic law, while that between the electropolishing rate and current density follows a near linear law. The relationship between the electropolishing rate and the time follows a near sigmoidal law. The practical spacing between anode and cathode is confirmed by the Hall bath experiment.     

形状记忆合金及应用

上世纪八十年代各种新型功能材料勃篷发展 ,形状记忆合金就是其中一种。形状记忆合金在医疗器械、家电装置、服装、汽车等领域得到广泛应用。目前已开发出十多种类的形状记忆合金 ,其中主要的是Ni Ti类形状记忆合金 ,该类合金具有变形大 ,性能稳定 ,耐久性优良 ,所以使用的最为普遍。Ni Ti二元系记忆合金 ,其原理是奥氏体相 R (菱面体 )相 (即马氏体相 ) ,而加铜的Ni Ti Cu(约 10 %质量 )三元系形状记忆合金是利用奥氏体相 斜方晶马氏体相比前者反应速度快 ,使用寿命长 ,主要使用在大量生产的弹簧 ,如用于空调装置中的风门片的传感器…     

电镀非晶铬与热处理

研究多种镀液在不同工艺参数条件下其镀铬层的结构特征,把20(Cu·ka)角的测定由文献上用X射线方法测列的85°扩大到145°,并在135°附近发现了新的结构特性,最后讨论了非晶镀层的形成原因及其耐蚀性。