Effect of liquid phase on the densification of tungsten-copper and molybdenum-copper pseudoalloys in sintering

The paper examines how the amount of the liquid phase influences the densification of loose W-Cu and Mo-Cu powder mixtures in liquid-phase sintering at 1200°C, with the content of the low-melting component ranging from 20 to 90 wt.%. It is observed that the density grows continuously with increasing amount of the liquid phase in both W-Cu and Mo-Cu systems. It is shown that samples sintered with a great amount of the liquid phase in the W-Cu and Mo-Cu systems retain their shape.     

Surface Phenomena and Interfacial Interaction at the Glass–Liquid Tin–Gas Phase Interface

We used the sessile drop method to study the temperature dependences of the density and surface tension of tin and liquid glass. We have studied the effect of the composition of the gas phase on the surface tension of the glass. We used the method of adjoining drops to determine the temperature dependence of the interfacial tension at the glass horbar; tin melt boundary. We have studied the effect of silicon, aluminum, iron, nickel, and manganese on the interfacial tension in the glass tin system. We have shown that in this system, these additives are not interface-active.     

Contact reaction of graphite with liquid iron and iron base melts

Conclusions A study was made, by a sessile drop technique involving simultaneous heating of the specimen and the base plate, of the interfacial reactions at the melt/graphite interfaces in the systems iron/graphite, iron-carbon-containing melt/graphite, iron-copper/graphite, iron-tin/graphite, iron-germanium/graphite, iron-gallium/graphite, and iron-aluminum/graphite. It is shown that the strength of the bond between the phase in contact in the systems investigated (except the system iron-aluminum/graphite) is determined by the work of adhesion linked with the departure of the system from a state of equilibrium. A relationship has been found between isotherms of wetting of graphite by the melts investigated and the effects of tin, germanium, gallium, and copper on the solubility of carbon in the relevant ternary systems. It is demonstrated that, for systems characterized by carbide formation (the system iron-aluminum/graphite), an isotherm of wetting of graphite by melts represents a complex dependence on melt composition.Translated from Poroshkovaya Metallurgiya, No. 6 (138), pp. 64–71, June, 1974.     

Investigation of Liquid-Phase Sintering in W ― Sn ― Si Pseudoalloys

The kinetics of reaction between particles of tungsten and silicon during liquid-phase sintering of W Si Sn pseudoalloys was studied. Specimen growth caused by the formation of tungsten disilicide was observed. The growth rate in the investigated ranges of time and temperature obeyed a linear law. The rate constant was determined, and also the activation energy of the process, which agreed with the standard heat of formation of WSi₂.     

The role of surface phenomena in powder metallurgy processes— A review

Conclusions A survey is presented of the role of surface phenomena at all stages of formation of sintered bodies by the methods of powder metallurgy.The properties of powders are shown to be determined chiefly by the surface properties. The role of surface phenomena in obtaining metal powder by various methods (reduction, electrolytic, mechanical, dispersion) is discussed in the paper. Surface phenomena are also important in pressing processes, and are a motive force in sintering processes. This is distinctly seen on sintering in the presence of the liquid phase and in impregnation processes. An attempt is made to link the strength of binding and microstructure in cermets with the surface properties of their components.     

Ge–Al and Sn–Al alloys capillary properties in contact with aluminum nitride

Experimental isotherms are presented for (1) wettability of AlN ceramics by Ge–Al and Sn–Al alloys, (2) surface tension and density of Ge–Al and Sn–Al alloys in the whole concentration range. Complex consideration of capillary characteristics of the melts under study is performed taking into account data available on thermodynamic activities of the melt components. The contact angle isotherms pass the minimum point for both systems. The contact angle value drops with Al addition more sharply for the Sn–Al system than for the Ge–Al alloys. This is in qualitative agreement with the higher thermodynamic activity of the components of the Sn–Al alloys. Sn decreases Al surface tension more than Ge. The reason for this is not only lower surface tension of Sn as compared to Ge, but also the higher thermodynamic activity of Sn in the Al melt.     

Advancing and Receding Contact Angles of Tin and Its Alloys on the Surface of a Solidified Glass Mass

The temperature dependence of advancing and receding contact angles has been determined for tin and its alloys with silicon, aluminum, and iron on the surface of a solidified glass mass. The advancing and receding contact angles of melts containing iron differ from those of melts containing silicon and aluminum. The difference becomes more pronounced in the low-temperature range as the iron content in the melt increases.     

V. N. Eremenko and the Development of Research into the Surface Properties of Molten Metals

The contribution of Academician V. N. Eremenko to the development of research into the surface properties of molten metals in the Ukraine is demonstrated. His name is connected with the methodical development of high-temperature methods for determining the surface characteristics of molten metals and alloys, obtaining a reliable mass of data about the surface properties of molten metals (including refractory and chemically active metals), and the study of temperature and concentration dependences of the surface properties of binary molten metals. The results are used in the physicochemical analysis of molten metals and development of ideas about the structure and properties of the surface layer at the melt-gas boundary.     

Surface-active additions in liquid metals

Summary The criteria of surface activity found in the literature are discussed in the paper. The differences in the specific heats of sublimation of the dissolved substance and solvent, as well as the differences of full potential barriers, are proposed as new criteria.The reliability of the criteria of surface activity was checked by the experimental data of over a hundred metal systems. The best criteria proved to be the differences between the free surface energies, full potential barriers and specific heats of sublimation of the dissolved substance and the solvent. The conjunction of these criteria is a reliable base for prognosis of the effect of dissolved elements on the surface properties of metal melts.