Structure formation and properties of molybdenum-base powder composites

Minakova, R. V.; Kresanova, A. P.; Lesnik, N. D.; Malyshenko, A. A.; Antonov, S. O.

doi:10.1007/bf00802738

Cited by 2 publications

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“…The parameters studied (i.e., the particle size and shape, the amount of liquid phase, the ratio of the surface energies at the phase boundaries, the wetting angle, etc.) The ordinates of the stress-strain curves were also observed to increase when nickel and cobalt were added to Mo-Cu composites [12]. The change in the phase composition and the structure of the composite as the result of alloying correlates with the level of the mechanical properties and the distinctive features of the fracture in bending tests in the temperature range 77-673 K. Analysis of the stress-strain diagrams (Fig.…”

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“…At the same we studied the structure and phase composition of the boundaries of the components of the composites, which were made by impregnating porous tungsten, molybdenum, or chromium compacts with copper or a melt of copper and an alloying element (the content of additives was determined with allowance for the results of experiments on spreading) by the method described in [11][12][13]. At the same we studied the structure and phase composition of the boundaries of the components of the composites, which were made by impregnating porous tungsten, molybdenum, or chromium compacts with copper or a melt of copper and an alloying element (the content of additives was determined with allowance for the results of experiments on spreading) by the method described in [11][12][13].…”

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confidence: 99%

“…A noteworthy feature of the powder materials studied is the fairly strong adhesion bond at the boundaries of the main structural components. 5c) occurs as a result of segregational enrichment of the surface of grains by impurity atoms (they can be detected by Auger electron spectroscopy [12]). As the temperature of the test is lowered the fraction of transcrystalline fracture of grains of the high-melting component increases.…”

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Contact interaction, structure, and properties of W(Mo, Cr)-Cu composites with additives

Minakova¹,

Lesnik²,

Kresanova³

et al. 1996

Powder Metall Met Ceram

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The results of research on the effect of additives on the adhesive characteristics and phase-boundary formation in W(Mo, Cr)-Cu systems are summarized. The distinctive features of structure formation and the properties of powder composites compacted in the presence of a liquid phase have been studied. Composites with optimal properties (high-temperature hardness, electrical conductivity, high adhesiveness, and stable structure) have been identified.In their quest for ways of solving problems of modern materials science researchers often turn to the potentialities of composites. By choosing the necessary components, determining their content, and determining the conditions of formation, we can obtain materials and products made of them with the required properties. This is how pseudoalloys of the W-Cu system, which are well known as electrical and structural materials, were produced. The present-day requirements imposed on those materials and the scarcity of tungsten propose either finding new materials based on elements of a different physicochemical nature or improving the properties of composite powder W-Cu pseudoalloys. The most effective method of strengthening the components and boundaries in such composites is by doping [1, 2]. When the above is taken into account, it is possible to define a number of other problems, the solution of which will contribute to the successful development of W(Mo, Cr)-Cu composites and will ensure the functional properties of high-current contacts and electrodes. Such materials are obtained primarily by impregnation [3]. Their properties depend on the volume fraction of the strong phase, the ratio of the properties of the high-melting and low-melting components, and the bond strength at their boundary [1]. A positive spreading coefficient is a necessary condition for attaining a perfect metal contact and maximum bond strength at the phase boundary in technological operations of impregnation and sintering with the participation of a liquid phase [4]. In the presence of oxides and other impurities the properties of the boundary deteriorate and the strength decreases. For examtale, the adhesion strength under shear at the boundary between tungsten and spectrally pure copper decreases from 196 to 32 MPa when a layer of oxides is present [5]. The decrease in bond strength at the phase boundary entails a drop in electrical conductivity, strength characteristics, etc. This paper reports the results of studies on the physicochemical conditions of contact interaction of condensed phases in W(Mo, Cr)-Cu systems with various additives. The data concerning the salient features of structure formation and some properties of powder composites of the same systems were obtained with the participation of a liquid phase. The content of the high-melting and low-melting components was determined in accordance with the conditions under which the strongest adhesion bond arose between the particles and the disperse system; the capillary forces were estimated by the method of [6] on a computer.Methods t...

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Contact interaction, structure, and properties of W(Mo, Cr)-Cu composites with additives

Minakova¹,

Lesnik²,

Kresanova³

et al. 1996

Powder Metall Met Ceram

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“…[7,9,11] Another approach is to add a small amount of Fe, Co, or Ni in the tungsten or molybdenum powder. [5,8,10,12,13] These elements help the wetting of copper on tungsten surfaces and improve the infiltration efficiency. However, the thermal conductivity of the compact is impaired by the alloying effect of these elements with the copper.…”

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“…[1][2][3][4][5][6] Another important application for W-Cu and Mo-Cu materials is electrical contacts, which need a combination of good wear resistance and thermal conductivity to alleviate the erosion and arcing problem incurred during power switching. [6][7][8][9] Since W-15Cu composites are frequently chosen for use in heat sinks and electrical contact materials, they were used in this study.…”

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The effect of tungsten particle size on the processing and properties of infiltrated W-Cu compacts

Wang

Hwang

1998

Metall Mater Trans A

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Three tungsten powders with average particle sizes of 8.7, 23.2, and 65.2 m were used to make W-15Cu compacts. The compacting pressure and sintering temperature were adjusted for each powder to attain the desired skeleton density. Sintered skeletons were then infiltrated with oxygen-free copper at 1200 ЊC in hydrogen and in vacuum. Results showed that as the tungsten particle size decreased, higher compacting pressures and sintering temperatures were required for the same desired skeleton density. The processing parameters and the tungsten particle size caused variations in the amount of closed pores and the W-W contiguity, which in turn resulted in different infiltrated densities and resistivities. Direct infiltration on green compacts was also examined, and higher infiltration densities and lower electrical resistivities were obtained compared to those obtained by infiltrating sintered compacts. These results are discussed based on infiltrated density, differences in microstructure, and the W-W contiguity.

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Structure formation and properties of molybdenum-base powder composites

Cited by 2 publications

References 1 publication

Contact interaction, structure, and properties of W(Mo, Cr)-Cu composites with additives

Contact interaction, structure, and properties of W(Mo, Cr)-Cu composites with additives

The effect of tungsten particle size on the processing and properties of infiltrated W-Cu compacts

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