Effect of conditions of preparation of nickel fibers extruded from powders on their strength properties. Part II

Conclusions In the manufacture of extruded fibers the main process parameters determining their strength properties are sintering temperature and sintering time up to 1 h. Structural factors adversely affecting the strength of extruded nickel fibers are porosity, interfaces between blocks, and ash residue inclusions. Raising the sintering temperature from 1200 to 1280°C decreases the porosity and amount of ash residue inclusions and smoothens out the fiber surface profile. Under these conditions the strength of the fibers rises from 0.5–0.7 to 0.7–0.8 of the ultimate strength of the cast metal annealed at the same temperature.Translated from Poroshkovaya Metallurgiya, No. 7(211), pp. 41–44, July, 1980.     

工艺条件对电积法制备铜粉的影响

采用不溶阳极电积法制备铜粉,研究了Cu²⁺质量浓度、硫酸质量浓度、电流密度、电解液温度和刮粉周期对电积过程和铜粉中位粒径的影响.结果表明:优化工艺为Cu²⁺质量浓度15 g·L^-1、硫酸质量浓度140 g·L^-1条件下,控制电流密度为1 800 A·m^-2、温度为35℃、刮粉周期为30min、循环流量为14 L·h^-1以及极距为4.5 cm,可得到高品质的铜粉,其粒度呈正态分布,微观形貌呈树枝状;增加铜离子质量浓度、硫酸质量浓度和电解液温度有利于降低槽电压;增加Cu²⁺质量浓度、电解液温度和刮粉周期有利于提高电流效率;大电流密度、高硫酸质量浓度和低Cu²⁺质量浓度有利于得到粉末粒度小的铜粉.     

Effect of a strengthening phase on the structure and some mechanical properties of electrolytic coatings based on nickel

An investigation was made of the composition, structure, microhardness, and tribological properties after thermochemical treatment of composite electrolytic nickel-based coatings with various additions. It was established that the mear resistance of nickel-boron-diamond coatings in sliding friction without lubrication depends upon the nature and amount of added inclusions, and the mechod of treatment. Materials Science Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 47–51, May–June, 1998     

工艺条件对溶液雾化氧化法制备Co_3O_4粉末的影响

以CoCl2·6H2O为原料,采用溶液雾化氧化法制备Co3O4粉末,对反应温度、溶液浓度、载气压力等工艺条件对产物粒子形貌及粒度分布的影响进行系统研究.结果表明,反应温度对Co3O4粉末的形貌和粒度都有影响,高温下粉末粒度较小,球形度较好,但温度过高会导致粒子团聚;COCl2·6H2O溶液的浓度对Co3O4粉末粒度也有影响,高浓度下所得Co3O4粉末的粒径较大;雾化压力增大,有利于得到颗粒分布均匀、分散性好的Co3O4粉末,但粉末粒度随之增大.在反应温度为850℃、CoCl2·6H2O溶液浓度为1.5 mol/L、雾化压力为1.5×10 5Pa的条件下,反应较完全,可制备物相单一的Co3O4粉末,产物为均匀分布的球形粉末,且粒度分布较窄.     

Effect of storage on the properties of ultrafine nickel and copper powders

Conclusions Storage of ultrafine powders under unfavorable conditions, in particular in air, adversely affects their processing properties, bringing about marked changes in their compressibility and sinterability. Storage in argon of technical purity does not offer effective protection to particles against surface oxidation. Storage of UFPs in the form of compacts of relative density 0.5–0.6 almost completely inhibits the powder oxidation process, and granulated powders produced by disintegrating compacts possess superior processing characteristics A simple method is proposed for estimating the oxygen content of a powder from the electrical resistivities of compacts.Translated from Poroshkovaya Metallurgiya, No. 10(274), pp. 74–78, October, 1985.     

Effect of the thermal component of barothermal treatment on the carbide phase component of a cast nickel alloy

Electron-probe microanalysis, scanning electron microscopy, and optical quantitative metallography are used to study the behavior of the carbides in a corrosion-resistant nickel superalloy during a barothermal action at a fixed pressure and exposure time (190 MPa and 210 min, respectively) and a sequential increase in the barothermal treatment (BTT) temperature from 1235 to 1320°C. The BTT temperature is found to significantly affect the chemical composition of the carbides, and this effect manifests itself in an increase in the titanium, molybdenum, or tungsten content and a decreases in the nickel or chromium content. The granulomteric composition of the carbide skeleton in the alloy is studied: it is found to depend substantially on the temperature of barothermal action. A model is proposed to describe the change in the chemical composition of the carbide structural constituent of a cast nickel alloy at a high pressure and temperature.     

水溶液湿化学法可控制备超细镍粉

采用湿化学法制备不同形貌的超细镍粉.通过改变氯化镍的浓度、氢氧化钠的浓度、氯化镍与水合肼和氢氧化钠的摩尔比、反应温度来控制超细镍粉的微观形貌;采用X衍射(XRD)和扫描电镜(SEM)对样品进行表征.结果表明,可通过改变物质之间的摩尔比、反应物的浓度和反应温度实现对镍粉的形貌和尺寸调控的目的.     

Processing effects on the grain-boundary character distribution of the orthorhombic phase in Ti-Al-Nb alloys

The grain-boundary character distribution of the orthorhombic (O) phase in Ti₂AlNb intermetallic alloys was investigated. The alloys were thermomechanically processed either above or below the bcc transus temperature. Using electron backscattered diffraction, the twin-related O-phase variant interfacial planes were identified and quantified. For the subtransus-processed samples, the equiaxed-O/equiaxed-O grain boundaries tended to primarily prefer 65-deg misorientations and secondarily prefer 90-deg boundaries. Of the 65-deg misoriented boundaries, which were preferentially rotated about [001], ∼40 pct contained (110) twin-related interfacial planes. The observations were rationalized by the α ₂-to-O phase transformation. It is suggested that for subtransus processing within the α ₂-containing phase regimes, the resulting heat-treated O+bcc microstructures evolve such that the O/O boundaries tend to exhibit distinct twin-related variants with misorientations between 55 and 65 deg. For a supertransus-processed alloy, it was found that approximately equal distributions of the six resolvable O variants were formed from the dominant parent bcc orientation. The resulting O/O boundaries tended to cluster at near-90-deg misorientations, which can be explained by the bcc/O orientation relationship. It is suggested that whenever the O phase primarily transforms from the bcc structure, the resulting O+bcc microstructures evolve such that the O/O boundaries tend to exhibit misorientations near 90 deg.     

Effect of the conditions of sintering of sodium-reduced tantalum powders on their characteristics

The effect of the granulation and heat treatment of sodium-reduced tantalum powders with a specific surface area of 2.5–3.6 m²/g on the bulk density, the powder flow time, and the specific surface area of the powders and the specific capacitance of the anodes made of them is studied. It is shown that heat treatment of a granulated powder in vacuum at 1100°C or in a mixture with magnesium at 800°C makes it possible to achieve the required powder flow time.