The thermodynamic activities of copper and iron in the system copper-iron-platinum at 1300°C

The vapor pressure of pure liquid copper and the partial pressures of copper exerted by six alloys in the system Cu−Fe, 12 alloys in the system Cu−Pt, and 44 alloys in the system Cu−Fe−Pt in the temperature range 1240°C to 1360°C have been measured by the Knudsen effusion technique, and the thermodynamic properties of the systems at 1300°C have been calculated from the vapor pressures. The system Cu−Fe shows large positive deviations from Raoultian ideality, and the system Cu−Pt shows large negative deviations. The activities of Fe in solid solutions in the system Cu−Fe−Pt at 1300°C have been calculated by Gibbs-Duhem integration of the activities of Cu. This paper is based on a presentation made in the T.B. King Memorial Symposium on “Physical Chemistry in Metals Processing” presented at the Annual Meeting of The Metallurgical Society, Denver, CO, February, 1987, under the auspices of the Physical Chemistry Committee and the PTD/ISS.     

Eutectic-gradient wear resistance in materials

New iron-base eutectic powder alloys have been developed (Fe−Mn−C−B−Si−Ni−Al−Sc, Fe−Mn−C−B−Si−Cr−Al−Sc, Fe−Mn−C−B−Si−Ni−Cr−Al−Sc) for wear-resistant coatings. The thermodynamic affinity for oxygen has been used in the technology for alloying the liquid with the necessary elements. Institute for Problems of Materials Science, Ukraine, National Academy of Sciences, Kiev, State University “L'vivska Polytechnika”, and Lublin Polytechical Institute, Poland. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(408), pp. 17–21, July–August, 1999.     

Thermodynamics of component interactions in Ge−Fe−Al liquid alloys

Partial enthalpies of mixing of aluminum in Ge−Fe−Al alloys along various radial sections in the ternary system with constant x_Ge/x_Fe ratio were determined with the aid of a high-temperature isoperibolic calorimeter. Integral heats of mixing were calculated from the partial heats for aluminum using Darken method. It was determined that alloy formation in the ternary system is accompanied by small exothermic heat effects. Component interactions in the binary Ge−Fe and Fe−Al systems have a marked effect on the thermodynamics of alloy formation in the ternary system. Taras Shevchenko National University, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(408), pp. 68–74, July–August, 1999.     

Equilibrium partition coefficients in iron-based alloys

Accurate relationships between equilibrium partition coefficients and solute concentration are required for the prediction of solute redistribution during solidification. Thermodynamic analyses are presented to relate these coefficients to fundamental thermodynamic quantities. Using the most accurate data available, partition coefficients are calculated for ten Fe−X (X=Al, C, Cr, Mn, Ni, N, P, Si, S, Ti) binary systems and compared with literature values. Equations are presented to allow for prediction of these partition coefficients as a function of temperature, as well as liquidus temperature as a function of composition. In addition, partition coefficient values are examined for the ternary systems Fe−Cr−C, Fe−Mn−Ni, and Fe−Ni−S. THOMAS P. BATTLE, formerly Graduate Research Assistant, The University of Michigan This paper is based on a presentation made in the T.B. King Memorial Symposium on “Physical Chemistry in Metals Processing” presented at the Annual Meeting of The Metallurgical Society, Denver, CO, February, 1987, under the auspices of the Physical Chemistry Committee and the PTD/ISS.     

Influence of the electrolysis temperature on the formation, composition, structure, and magnetic properties of highly dispersed iron and iron-nickel alloy powders

The influence of the electrolysis temperature on the formation, chemical and phase composition, structure, and magnetic properties of highly dispersed iron and iron-nickel (50∶50) powders is investigated. The optimal thermal conditions are determined for the production of powders with micron-sized particles in a two-layer electrolytic bath from concentrated solutions of electrolytes. Institute of Colloid Chemistry and Water Chemistry, UkranianAcademy of Sciences Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5/6(395), pp. 37–42, May–June, 1997.     

Magnetic alloys in nanoscale biomaterials

Fe−Co composition gradient and Fe−Pt multilayer alloy films were tested as catalysts for groving vertically aligned carbon nanofibers (VACNFs) by plasma-enhanced chemical vapor deposition (PECVD). The Fe−Co film yielded nanofibers with alloy tips in a wide compositional range varying from 8.15 pct Fe at the Co-rich end to 46.29 pct Fe in the middle of the wafer as determined by energy-dispersive X-ray analysis. Two Fe−Co cubic phases (SG Pm3m, were identified by preliminary X-ray diffraction (XRD) measurements. Magnetic measurements showed a substantially greater hysteresis loop area and coercivity in Fe−Co catalyst nanoparticles as compared to the asdeposited Fe−Co film. The Fe−Pt film did not break into FePt alloy nanoparticles under the applied processing parameters and thus the utility of FePt as a VACNF catalyst has been inconclusive. I.M. ANDERSON, formerly with the Microscopy, Microanalysis, Microstructures Metals and Ceramics Division. Oak Ridge National Laboratory This article is based on a presentation made in the symposium entitled “Fourth International Alloy Conference,” which occurred in Kos. Greece, from June 26 to July 1, 2005, and was sponsored by Engineering Conferences International (ECI) and co-sponsored by Lawrence Livermore National Laboratory and Naval Research Laboratory, United Kingdom.     

Obtaining Fe—Ni—Co—Ti alloys having a thermoelastic martensite transformation

Using powder metallurgy methods, we have produced Fe—Ni—Co—Ti alloys that have a thermoelastic martensive transformation, which is the basis of the shape-memory effect manifested by such materials. Since pores are believed to improve the shape memory, specifically the reversible nature of the strain, attention was focused on development of the technology and investigation of the characteristics of porous Fe—Ni—Co—Ti alloys. The problems that arise during sintering of such alloys from sputtered powders are due to the chemical inhomogeneity of the initial structure and of the structure formed when the liquid phase appears. Various forms of activation, such as cyclic sintering and a stepped increase in temperature, were used to prevent the liquid phase from appearing. The properties of Fe—Ni—Co—Ti alloys with a shape memory effect can be improved if the porosity is increased by obtaining larger powder grains with a more complicated shape. Materials Science Institute, Ukrainian Academy of Sciences Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 79–85, January–February. 1997.     

Production of Nd-Fe-B alloy powders using high-pressure gas atomization and their hard magnetic properties

Fine spherical Nd−Fe−B powders with a tetragonal Nd₂Fe₁₄B phase have been produced by high pressure argon or helium atomization. The average size defined by 50 pct cumulative weight fraction is as small as about 25 μm. The Curie temperature of the powders is about 580 K and the intrinsic coercivity (iH _c ) of the bonded products made from the powders increases with decreasing particle size and reaches about 0.581 MA/m for the powder below 25 μm diameter. TheiH _c value increases with an increase in the cooling rate by helium atomization as well as with an increase in neodymium and boron content to 18 at. pct Nd and 12 at. pct B with the highestiH _c value reaching 0.716 MA/m. Annealing in the range of 773 to 1073 K gives rise to a further increase ofiH _c to 1.035 MA/m. The highiH _c value is promising for practical use as isotropic bonded powder magnets. The increase of magnetization for the bonded powder magnets takes place rapidly and the behavior is similar to that for sintered Nd−Fe−B magnets, in goods contrast to a sluggish increase of magnetization for the bonded Nd−Fe−B powder magnets made from the comminuted powders of melt-spun ribbon. From the magnetization behavior, it was presumed that the generation of the large intrinsic coercivity is due to the difficulty of the nucleation of reverse domain rather than the pinning of domain walls.     

Properties and structure features of nanocomposite powders based on SiC

Features of the synthesis of SiC−Si₃N₄−Si₂N₂O composite powders are studied. The characteristics of the powders are examined on the basis of x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The structure features and mechanical properties of a ceramics formed on the basis of the synthesized powders are also studied. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Traslated from Poroshkovaya Metallurgiya, Nos. 7–8(408), pp. 12–16, July–August, 1999.     

Secondary metals as raw materials for powder metallurgy

The possibility of using new technology based on the disintegrator milling method for utilizing metal chips of cast iron, high-alloy steels, nonferrous alloys (Al−Cu, Zn−Al, Cu−Zn), and used parts of hard metals based on tungsten carbide was investigated. The powders produced were used for corrosion- and wearresistant coatings having properties similar to those of traditional powders. Tallinn Technical University, Republic of Estonia. Published in Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 1–6, January–February, 1999.     

High-dispersion iron powders produced by the thermochemical method

The problem of producing high-dispersion iron powders is very complicated because of the fact that these powders are highly pyrophoric and, consequently, the number of methods of production of these powders is limited. Another difficulty is that the majority of these methods do not make it possible to vary the properties of microcrystals in the required range and this greatly restricts the application of powders. Institute of Colloidal Chemistry of Water, National Academy of Sciences of the Ukraine. Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 1–4, May–June, 1998.     

Highly dispersed composite iron—Copper powders obtained from oxalates by a thermochemical method

The preparation of highly dispersed composite iron—copper powders with various concentrations of copper from mixed iron and copper oxalates was studied. The physico-chemical properties of the powders were determined. The powders were corrosion resistant, hydrophilic, practically monodispersed, bacteriocidal and tolerated the sterilization at elevated temperatures. Their magnetic properties could be regulated in the process of forming the initial components. Such powders can be useful in medicine, biology and technology. Institute of Colloid and Water Chemistry, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(402), pp. 1–4, July–August, 1998.     

Finely divided Fe-Co-Ni powders made by a thermochemical method

It is shown to be possible to make finely divided Fe-Co-Ni powders with given physicochemical properties. Iron, cobalt, and nickel oxalates have been made by chemical methods. Hydrogenous media have been used in the thermal decomposition of the iron oxalates to give finely divided powder that are nonpyrophoric and corrosion resistant and which have high contents of the metallic phase and given magnetic properties. These powders have been used in sealing composites for pipelines, and also as fillers in lacquers and magnetic liquids for general purposes.Institute for Colloid Chemistry and Water Chemistry, Ukrainian National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(384), pp. 111–113, March–April, 1996. Original article submitted June 20, 1994.     

The kinetics of oxidation of iron-silicon and iron-aluminum alloy melts by pure oxygen or oxygen-bearing gases

The kinetics of oxidation of Fe−Si and Fe−Al melts by pure oxygen, and that of pure Fe by He−O₂, N₂−O₂, or Ar−O₂ mixtures have been investigated by a modified Sieverts' method at 1600°C. Considerable decrease in the oxidation rate has been observed for the alloy melts containing a few percent of Si or Al since formation of a silica- or alumina-rich oxide layer on the melts prevents further progress of the exothermic chemical reaction. The oxidation rate for melts high in Al has been considered to be limited by the diffusion of ions through the oxide layer. Addition of diluents to O₂ markedly and continuously decreases the oxidation rate of a pure Fe melt. The latter rate has been show to be controlled by the diffusion of O₂ across the gaseous boundaries at gas/melt interfaces.     

Elastic constants of martensite

The elastic constants of Fe−Ni−C martensite are increased by retained austenite. Also, nickel markedly decreases the elastic constants of such martensite. Therefore, to properly evaluate the effect of carbon on the elastic constants of Fe−Ni−C martensite, it is necessary to first correct for both retained austenite and nickel content. When these corrections are made, both the Young's modulus and the shear modulus of Fe−Ni−C martensites. decrease with increasing carbon content, in agreement with earlier work on Fe−C martensites. thus, an increased lattice stiffness cannot be used to explain the high strength of martensite.     

Deformation of materials based on thermally expanded graphite

Strain and strength in uniaxial compression have been examined for specimens with various densities made by uniaxial pressing of thermally expanded graphite powders, which have been produced by the heat treatment of intercalated graphite compounds. Low-density graphite specimens formed at 600°C have the highest strain resistance. Surface Chemistry Institute, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurigya, Nos. 5–6, pp. 18–23, May–June, 1998.     

A thermodynamic analysis of the Fe−C and Fe−N phase diagrams

The experimental information on the Fe−C and Fe−N phase diagrams are evaluated in order to be able to recalculate the phase diagrams in close agreement with the experimental information available. Analytical expressions for the Gibbs energy of pure iron in the bcc and liquid states relative to the fcc state have been obtained by means of power series expansions. A set of parameters describing the Gibbs energy of the individual phases is presented.     

Precipitation-strengthened austenitic Fe−Mn−Ti alloys

The precipitation of intermetallic compounds in the Fe−20Mn−2Ti and Fe−28Mn−2Ti alloy systems has been investigated over the temperature range 700 to 900°C by hardness measurements, optical and scanning electron microscopy, and X-ray diffraction. In both systems only the equilibrium Laves phase was observed. The precipitate was identified as C14(MgZn₂) type hexagonal Laves phase with a chemical composition close to Fe₂ (Ti, Mn). In an as-annealed sample precipitation occurred in a heterogeneous manner, predominantly along grain boundaries. The effect of a cold deformation between the solution annealing and aging processes was also investigated. In addition to a high density of dislocations, martensitic phases were induced by deformation: a γ→∈ transformation occurred in the Fe−28Mn−2Ti alloy while a γ→α′ transformation was predominant in the Fe−20Mn−2Ti alloy. Subsequent aging was conducted at temperatures above theA _f . A large number of very fine precipitates formed randomly in the matrix after a short aging period. This cold work plus aging treatment resulted in an increase in yield strength. The enhancement of mechanical properties is due to the randomly distributed precipitates combined with the high defect density and fine substructure.     

Finely dispersed Si3N4−SiC powders and materials based on them

The objectives of the present research were to investigate the preparation of homogeneous ultrafine composite Si₃N₄−SiC powders by a plasmochemical process and the properties of ceramics produced from them. The chemical and phase compositions of the powders depended on the particle size of the initial powder, silicon input rate, and ratio of ammonium and hydrocarbon flow rates. The particle size and specific surface area of the compounds depended on the concentration of particles in the gas jet, and the cooling rate of the products. Composite powders containing from a few up to 90 mass % SiC, with specific surface areas of 24–80 m²/g and free silicon and carbon content less than 0.5 mass % were obtained. The main phases present were α-Si₃N₄, β-Si₃N₄, β-SiC, and X-ray amorphous Si₃N₄. Dense materials were prepared both by hot pressing at 1800°C under a load of 30 MPa and gas-pressure sintering at 1600–1900°C under a pressure of 0.5 MPa nitrogen. The plasmochemical composites had smaller pore sizes, were finer grained, and densified more rapidly than materials sintered from commercial powders. Institute of Inorganic Chemistry, Latvian Academy of Sciences, Salaspils. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 7–12, January–February, 1999.     

Phase equilibria for iron-rich Fe−Cu−C alloys: 1500 to 950°C

Isothermal sections for the iron rich corner of the Fe−Cu−C system have been constructed at 1500, 1450, 1200, 1172, 1150, 1000, and 950°C. A ternary invariant point exists at 1172°C where an iron rich liquid, a copper rich liquid, austenite, and graphite coexist. The iron rich liquid contains 3.7 wt pct Cu and 4.0 wt pct C. The austenite contains 7.3 pct Cu and 1.6 pct C. The copper rich liquid contains 2.4 pct Fe, and apparently very little carbon. The diagrams are used to explain the phenomena of “inverse segregation” that occurs during the solidification of iron rich Fe−Cu−C alloys. KRISHNA PARAMESWARAN, formerly Metallurgy Graduate Student, University of Missouri-Rolla KENNETH METZ, formerly Metallurgy Graduate Student, University of Missouri-Rolla