熔渗铜用多孔金刚石坯体的制备

高体积分数金刚石颗粒增强Cu基复合材料由于硬度高导致其难以加工成形。采用粉末注射成形制备多孔金刚石预成形坯和Cu熔渗相结合的工艺可以实现金刚石/Cu的近净成形。本文对经过表面镀铬再镀铜的金刚石粉末注射成形涉及的关键工艺,包括粘结剂的选择、注射成形工艺过程、烧结工艺等进行研究。结果表明,采用成分为70%石蜡+25%高密度聚乙烯+5%硬脂酸的粘结剂作为金刚石粉末注射成形的载体时,喂料具备优异的综合流变性能,同时可以获得较高的固相体积分数。采用上述配方的粘结剂,最佳的注射温度为165～175℃,注射压力为80～90 MPa。脱脂金刚石预制坯最佳的烧结条件为:烧结温度1 050℃,保温时间25 min,此时坯体的强度达到10 MPa,孔隙基本全部为开孔隙。     

Influence of impurities on the properties of powder metallurgy and cast iron-manganese alloys

Translated from Poroshkovaya Metallurgiya, No. 6(306), pp. 56–61, June, 1988.     

医用多孔钛及钛合金的研究进展

医用钛及钛合金材料由于能提高材料的骨引导作用,有利于骨组织的长入促进骨性结合而在临床上得到了越来越广泛的应用.文章从医用钛及钛合金材料的发展、成型方法及表面改性进行了概述.     

Cold shortness and nature of failure of iron-manganese powder alloys

Conclusions The level and nature of variation of impact toughness in the iron-manganese powder alloys are similar to the vacuum-melted cast alloys. The lowest cold brittleness threshold was recorded for the alloys with 20–23% Mn (determined at –253°C) containing the maximum amount of -martensite and positioned at the boundary of the + + and + regions. Brittle fracture in these alloys takes place by the intercrystalline mechanism, and the inclusions, depending on their composition, size, and distribution, can both support crack propagation and delay this process. The possible mechanisms of failure of the powder materials are proposed on the basis of the literature data and own experimental investigations.Translated from Poroshkovaya Metallurgiya, No. 12(300), pp. 77–83, December, 1987.     

Increasing the life of molds for casting copper and its alloys

The work of the molds intended for casting copper and copper alloys in semicontinuous casters for producing flat billets is considered. It is shown that, to increase the resistance of mold plates, the inner space of the mold should have a taper shape toward the casting direction and take into account the shrinkage of the linear dimensions of the ingot during its motion in the mold. The taper shape increases the intensity and uniformity of heat removal due to close contact between the ingot and the mold inner surface. Testing of new design molds under industrial conditions demonstrates that their resistance increases by a factor of 4.0–4.5. The taper effect of the mold plates is much more pronounced in their narrow faces.     

Nanotechnology for copper and copper alloys

This article surveys and analyzes the literature data on nanotechnologies for copper and copper alloys. It describes the main methods used to obtain nanomaterials, including powder metallurgy, crystallization from the liquid state with a controlled rate of cooling, intensive plastic deformation, dispersion hardening, and dispersion strengthening with internal oxidation. Preference is given to nanophase materials in the discussion. __________ Translated from Metallurg, No. 8, pp. 40–46, August, 2007.     

Modeling the kinetics of infiltration of porous powder materials with melts

The infiltration of porous materials was analyzed using a three-dimensional model of the pore structure as a spatial lattice formed by monospherical particles. Coordination number, size, porosity, and interparticle contact area were taken into account. As examples, the kinetics of infiltration of poured titanium and steel powders, and also of sintered materials were calculated. Calculated and experimental results were found to be in satisfactory agreement.     

稀土对铜及铜合金的影响

论述稀土元素对铜及铜合金中的物理化学作用,介绍稀土对合金的组织、工艺性能、力学性能、耐蚀性能、耐磨性能以及焊接性能等方面的影响,总结了稀土在铜及铜合金中的开发应用.     

Atmospheric corrosion of copper and some copper alloys

Abstract

Two-year atmospheric corrosion tests in an urban environment were conducted on specimens of copper, Muntz metal, and copper-zinc-aluminum alloys. X-ray diffraction and X-ray spectrographic studies were made of the films on the top surface and underside of the exposure coupons which were exposed facing south but inclined at a 45° angle to the vertical. Differences between the two surfaces are attributed to the leaching action of rain as well as the possible effect of direct sunlight. The corrosion products of copper were found to consist predominantly of Cu₂O, but also included a substance of undetermined composition, copper chloride and basic copper chloride. The zinc-containing alloys formed similar products, along with zinc sulphates, and showed considerable dezincification. A preoxidation treatment improved the tarnished appearance of the ternary alloy.

Résumé

Des essais de corrosion atmosphérique en milieu urbain ont été exécutés sur du cuivre, du métal Muntz et des alliages Cu-Zn-Al. Les échantillons étaient placés à un angle de 45°, face au sud et des mesures de diffraction aux rayons-X et de spectrographie X ont été faites sur chacune des faces. Les differences entre les deux faces d'un même échantillon peuvent étre attribuables à la pluie et peut-être aussi au solell. Les produits de corrosion du cuivre sont surtout formés de Cu₂O et également du chlorure de cuivre, du chlorure basique de cuivre et un composé non identifié sur les alliages contenant du zinc des produits semblables se sont formés avec aussi des sulfures de zinc; on y notait aussi une dézincification. Dne oxydation avant les essais améliorait l'apparence finale des alliages ternaires.     

An electrochemical study on the dissolution of gold and copper from gold/copper alloys

The dissolution behavior of gold and copper from their elemental states and from gold/copper alloys in cyanide solutions has been investigated using a rotating-disc electrode. The anodic and cathodic reactions were studied separately, and the resulting polarization curves were combined to examine the overall dissolution reactions. The dissolution rate of pure gold in the aerated cyanide solutions was inhibited by the anodic passivation on the gold surface, whereas the dissolution rate of pure copper was found to be mass-transfer controlled. On the other hand, the dissolution of gold and copper from the alloys was partially controlled by electrochemical reaction and largely by mass transfer.     

Cavitation erosion of copper and copper-based alloys

Cavitation erosion studies of five multiphase copper-based alloys for a screw propeller application and of three α-solution alloys of comparative purpose have been carried out to determine the resistance of the alloys to cavitation erosion and to understand the influence of the microstructure and/or composition of the alloys on the morphology of erosion damage. The experiments were conducted using a vibratory system. Erosion rates were measured, and the mechanism of damage under cavitation action was studied. No correlation between the cavitation erosion resistance (CER) and the mechanical properties of the alloys has been found. However, a good correlation between the resistance and work-hardenability, defined by means of stacking-fault energy (SFE), being a chemistry-dependent property, has been established for the α-solution alloys. A better CER can be expected for a lower SFE and higher work-hardenability. The resistance of the multiphase alloys in terms of chemical composition and mode of damage was discussed. An advantageous influence of nickel and aluminum and a low effectiveness of zinc on cavitation resistance have been outlined.     

Modeling creep and fatigue of copper alloys

This article reviews expressions to quantify the thermal creep and fatigue lifetime for four copper alloys: Cu-Ag-P, Cu-Cr-Zr, Cu-Ni-Be, and Cu-Al₂O₃. These property models are needed to simulate the mechanical behavior of structures with copper components, which are subjected to high heat-flux and fatigue loading conditions, such as molds for the continuous casting of steel and the first wall in a fusion reactor. Then, measurements of four-point bending fatigue tests were conducted on two-layered specimens of copper alloy and stainless steel, and thermal ratchetting behavior was observed at 250 °C. The test specimens were modeled with a two-dimensional elastic-plastic-creep finite-element model using the ABAQUS software. To match the measurements, a primary thermal-creep law was developed for Cu-0.28 pct Al₂O₃ for stress levels up to 500 MPa and strain rates from 10⁻⁸ to 10⁻² s⁻¹. Specifically, (s⁻¹)=1.43×10¹⁰ exp (−197,000/8.31 T(K)) (σ(MPa))^2.5 (t(s))^−0.9.