Composition and thermodynamics of the surface layer of binary melts based on iron,cobalt, and nickel

The composition, thickness, thermodynamic activities of components, Gibbs energy and excess energy of formation of the surface layer on binary melts of iron, cobalt and nickel-based alloys with different interatomic interactions were evaluated with the aid of data from the literature and the authors measurements of the concentration dependence of the surface tension and molar volume.     

Determination of the Composition of the Surface Layer of Binary Metal Alloys

We have analyzed the effect of various parameters (surface tensions of the components, molar volumes of the components and the solution, compression and depression in alloy formation, activity coefficients of the components in the melt) on the shape of the surface tension isotherm as a function of the surface layer composition. We compare the analysis results with experimental data. We propose a method for estimating the composition of the surface layer based on a model assuming an additive variation in the surface tension of the solution as a function of the composition of the surface layer. We have calculated the concentration of the surface-active component in the surface layer of melts in the systems Ge - Sn, Ge - Pb, and Ge - Bi.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 60–67, January–February, 2005.     

Compaction Kinetics with Liquid-Phase Sintering of W – Ni – Sn Pseudoalloys

A kinetic equation for compaction with liquid-phase sintering is found on the basis of rheological sintering theory. Kinetic coefficients of the equation are determined from physicochemical properties of a dispersed system and its components. Compaction kinetics are studied for the system W – Ni – Sn where the liquid phase is eutectic alloy Ni – Sn with the greatest nickel content. It is shown that experimental results are in good agreement with those obtained by the kinetic equation on the coordinates porosity – time. Diffusion coefficient is evaluated for tungsten in melt (67.5 mass% Ni + 32.5 mass% Sn): at 1200°C it is 0.113·10_–5 cm₂/sec for grain diameter L ₀ = 3 μm. Time dependences are also obtained for the compaction rate and viscosity of the pseudoalloys studied.     

Densification kinetics of W-Fe-Sn pseudoalloys in liquid phase sintering

The densification kinetics in liquid phase sintering of W-Fe-Sn powder composites containing 90 wt.% of a refractory component and 10 wt.% of a low-melting component is strongly dependent on the iron content in the melt. As the iron content in composites increases, the concentration dependence of their densification shows a maximum. Samples containing more than 1.5 wt.% Fe grow intensively because of the formation of W₆Fe₇ intermetallide whose decomposition temperature is higher than that of liquid phase sintering. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 22–29, 2007.     

Wetting of Al2O3-Based Oxide Ceramics by Molten Aluminum

The temperature dependence has been determined for the wetting by molten aluminum of materials based on aluminum oxide (polycor and corundum). A temperature range has been identified in which the wetting increases significantly. There is no effect on the wetting characteristics of these oxide materials from the addition to the aluminum of up to 25% silicon, 33% copper, or 6% nickel.     

Noncontact strain gauge in a high-temperature dilatometer

Translated from Izmeritel'naya Tekhnika, No. 3, pp. 25–27, March, 1991.     

Densification kinetics of Mo-Ni-Sn composites in liquid-phase sintering

The paper examines the densification kinetics in liquid-phase sintering of Mo-Ni-Sn samples containing 90 wt.% of molybdenum and 10 wt.% of liquid phase in which the content of nickel varies from 5 to 67.5 wt.%. The samples continuously densify with increasing nickel content. It is examined how the amount of the 28 wt.% Ni-72 wt.% Sn liquid phase influences the densification kinetics of samples with varying content of molybdenum. The densification parameter increases with the amount of the liquid phase.     

Microstructure of W - Ni - Sn Composites in Relation to Amount of Liquid Phase on Sintering

Microstructure transformation is examined for W - Ni - Sn composites made by liquid-phase sintering at 1200 °C for 1 h; the liquid phase was a eutectic containing 67.5 mass% Ni and 32.5 mass% Sn. There is a nonmonotone dependence of the tungsten grain size in the sintered composites on the volume proportion of liquid phase in the range 6.7–36.8%. The mean grain size in relation to volume proportion of liquid phase in liquid-phase sintering is calculated from rheological sintering theory. The form of the empirical function f(v) is quantitatively demonstrated, which determines the rate of tungsten grain growth on liquid-phase sintering and is dependent on the proportion of matrix in the composite and the size of the liquid phase layer. __________ Translated from Poroshkovaya Metallurgiya, Nos. 7–8(444), pp. 53–57, July–August, 2005.     

Effect of liquid phase on W-Ni-Sn and W-Co-Sn pseudoalloys in liquid-phase sintering

The effect of the liquid phase of different compositions on the compaction of W-Ni-Sn and W-Co-Sn pseudoalloys in liquid-phase sintering is studied. It is established that the compaction of W-Ni-Sn pseudoalloys enhances with increasing liquid-to-solid phase volume ratio. Changes in volume of W-Co-Sn pseudoalloys with a varying amount of the liquid phase in sintering depend on the melt composition: the compaction increases for 20 wt.% Co and 80 wt.% Sn and the samples grow regardless of the liquid phase amount for 50 wt.% Co and 50 wt.% Sn. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 3–10, 2007.