Effect of carbon on the surface properties of liquid iron

Conclusions A study was made of the effects of temperature and composition on of Fe-C melts. It was found that, in the hypoeutectic range of compositions, the polytherms of of the melts investigated are not straight lines and are characterized by a positive temperature coefficient of . Carbon exhibits surface activity in liquid iron. A hypothesis is advanced in explanation of this phenomenon. The wetting of alumina by Fe-C melts was investigated at various carbon concentrations and temperatures. Raising the carbon content improves wetting in the system (Fe-C)_L-A1₂O₃.Translated from Poroshkovaya Metallurgiya, No. 10 (118), pp. 57–61, October, 1972.     

Effect of interaction between the structural components of W-Co-Sn pseudo-alloys on the kinetics of their compaction during liquid-phase sintering

Compaction kinetics during liquid-phase sintering of W-Co-Sn powder composites containing 90 mass% refractory component and 10 mass% readily-melting component is studied. It is established that compaction kinetics depends markedly on cobalt content in the melt. Specimens with a cobalt content up to 3 mass% at 1200 °C (in the nonisothermal heating stage) undergo an increase in volume, and then they are compacted at a rate typical for liquid-phase sintering. The nonuniform nature of compaction is observed with an increase in cobalt in the test composites. Specimens with a cobalt mass fraction of more than 2% (cobalt content with three-phase equilibrium) experience considerable additional growth due to formation of the intermetallic compound W₆Co₇ whose decomposition temperature exceeds the liquid-phase sintering temperature.     

Study of the impregnation of refractory carcasses with molten metals by filming the free meniscus

The basis of the method is monitoring liquid consumption. This is recorded by successive cine pictures of the shape of the liquid meniscus between a support and a porous specimen. Liquid volume, consumption, and penetration rate are calculated for each frame using the Guldin theorem.Institute of Materials Science Problems, Ukrainian National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 57–60, July–August, 1996.     

Free Surface Energy as a Criterion for the Sequence of Intermetallic Layer Formation in Reaction Couples

We propose a new criterion for predicting the first growing phase and the phase growth sequence in a binary system in which several compounds are formed: the free surface energy of the components and compounds. The compound with the lowest free surface energy is the first to grow. The sequence of formation for layers of the other possible compounds is determined by the values of their free surface energies. If compounds exist in the system with close surface energies, the compound with fewer atoms in the unit cell is more likely to form first. We propose using the S. I. Popel'-V. V. Pavlov equation to calculate the free surface energy of hard intermetallics. We demonstrate the high predictive power of the proposed criterion.     

Surface Properties of Manganese – Tin Liquid Alloys

We used the sessile drop method to study the temperature and concentration dependences of the density and surface tension of melts in the manganese – tin system. The density polytherms are linear dependences which are consistent with those calculated by the additivity rule for the specific volumes of the pure components. The temperature dependences of the surface tension are also linear and their temperature coefficient changes from negative values for tin-rich melts to positive values for melts with high manganese content. The surface tension isotherm is satisfactorily described by the Popel-Pavlov equation. We calculated the composition of the surface layer of the studied melts as a function of the composition of the bulk phase. We have shown that the model for the surface layer of melts in the Mn – Sn system at 1300°C is close to monolayer.     

Surface Parameters of Carbon-Saturated Nickel-Copper Liquid Alloys

The sessile drop method has been used to determine the temperature dependence of the surface tension for nickel ― copper liquids saturated with carbon. The surface-tension polytherms are fitted to equations with negative temperature coefficients for straight lines. The concentration dependence of the surface tension passes through a minimum. The surface activity of carbon in these liquids is positive.     

Enthalpy of Mixing and Excess Volume of Binary Metallic Melts of Eutectic Systems

The enthalpies of mixing H and excess volumes V were analyzed in alloy formation from binary metallic eutectic systems. Three types of systems can be distinguished: I with H > 0, V > 0; II with H > 0, V 0; III with H < 0, V 0. The hypothesis is discussed that another yet unstudied group IV exists in which H < 0, V < 0.     

Calculation of the surface layer composition in binary metallic melts

The model-thermodynamic equation of S. I. Popel’ and V. V. Pavlov was used to predict the composition of the surface layer of binary metallic melts. The surface concentrations calculated from this equation were in better agreement with experimental data than those calculated from Gibbs adsorption equation. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 60–69, May–June, 2000.     

Features of W - Ni - Sn Pseudoalloy Compaction during Sintering in the Presence of a Liquid Phase

The kinetics of compaction with liquid-phase sintering for pseudoalloys of the system W - Ni - Sn are studied with molten Ni - Sn as the liquid phase. Experimental data are satisfactorily described by a kinetic equation on porosity - time coordinates. Time dependencies for compaction rate and viscosity are established for these alloys.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 17–24, March–April, 2005.