Researches of 90W-7Ni-3Fe (WHA) sinters structure, produced by resistance method and investigated after plastic deformation
Tomasz Majewski Wojskowa Akademia Techniczna, ul. Kaliskiego 2, 00-908 Warszawa
Quarterly No. 2, 2005 pages 58-62
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abstract Tungsten heavy alloys, i.e. tungsten based metal-matrix composites are characterized by unique properties, because except their high hardness, strength and density, they also possess excellent ductility, impact strength, machinability and corrosion resistance. This combination of properties makes these alloys suitable for a wide range of engineering applications, e.g. in the mechanical engineering and in the armament and aviation as well. This paper contains results of investigations of the 90W-7Ni-3Fe composites obtained by the traditional and resistance methods. The powder compact was heated directly by the applied current in the resistance method and a high heating rate and consequently a short sintering time, which can be achieved. In this paper, the dependence of sintering method and sintering parameters on structure W-Ni-Fe alloys was determined. It was found that increase of sintering time during resistance sintering (Figs 2-4 and Table 1) causes increase of growth rate of tungsten particle and their elongation. In this way the microstructure with very long tungsten grains is observed (Fig. 3), similar to microstructure after plastic deformation (Fig. 5). At low strain rate (quasistatic) the grains of tungsten alongation is equal in the whole investigated sinters. It was found that there are numerous bands of deformation in the samples investigated under dynamic conditions (Fig. 6). The study also presents relationship between hardness and strain. The increase value of hardness is higher at high strain rate. Moreover it was found that hardness of the resistance sinters is higher for various strains than produced by the traditional method (Fig. 10). Key words: composites with tungsten matrix, heavy sinters, resistance sintering