Abstract

KUMARI, Anjali et al. The effect of fine W precipitates in matrix phase on mechanical properties of tungsten heavy alloys. J. appl. res. technol [online]. 2022, vol.20, n.4, pp.487-501.  Epub May 05, 2023. ISSN 2448-6736.  https://doi.org/10.22201/icat.24486736e.2022.20.4.1357.

Tungsten heavy alloys 90W-7Ni-3Co (WNC alloy) and 89.6W-6.2Ni-1.8Fe-2.4Co (WNFC alloy), produced using liquid phase sintering followed by thermo-mechanical processing, were investigated for microstructure and mechanical properties. 90W-7Ni-3Co alloy processed following a cyclic heat treatment showed fine tungsten precipitates in the matrix. The alloy, when heat treated at 850°C (the lower temperature of cyclic treatment), formed a W-rich intermetallic phase in the matrix that subsequently dissolved during high temperature (1150°C) solution treatment leaving behind fine W precipitates. On the other hand, the cyclic treatment (850°C/1150°C) of 89.6W-6.2Ni-1.8Fe-2.4Co alloy did not result in precipitation of fine W in the matrix phase. Therefore, the alloy was given a standard solution treatment (1150°C/WQ) resulting in matrix showing a clean microstructure devoid of any precipitates. Both the alloys were subjected to a two stage swaging with intermediate heat treatments. 90W-7Ni-3Co alloy exhibited superior strength, but lower elongation to failure and impact toughness as compared to 89.6W-6.2Ni-1.8Fe-2.4Co alloy. Microstructure-property correlation was undertaken to elucidate the effect of enhanced W dissolution and fine W precipitates (in the matrix) on mechanical behaviour of the alloys investigated.

Keywords : W-Ni-Co alloy; precipitate; dislocation; yield strength.

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