Microstructural control of and mechanical properties of mechanically alloyed tungsten heavy alloys |
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Authors: | Ho J Ryu Soon H Hong Sung Lee Woon H Baek |
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Affiliation: | (1) Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 373-1 Kusung-dong, Yusung-ku, 305-701 Taejon, Korea;(2) Agency for Defense Development, Yusung-ku, P.O. Box 35, 305-600 Taejon, Korea |
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Abstract: | 93W-5.6Ni-l.4Fe tungsten heavy alloys with controlled microstructures were fabricated by mechanically alloying of elemental
powders of tungsten, nickel and iron by two different process routes. One was the full mechanical alloying of blended powders
with a composition of 93W-5.6Ni-l.4Fe, and the other was the partial mechanical alloying of blended powders with a composition
of 30W-56Ni-14Fe followed by blending with tungsten powders to form a final composition of 93W-5.6Ni-l.4Fe. The raw powders
were consolidated by die compaction followed by solid state sintering at 1300°C for 1 hour in a hydrogen atmosphere. The solid
state sintered tungsten heavy alloys were subsequently liquid phase sintered at 1445∼1485°C for 4-90 min. The two-step sintered
tungsten heavy alloy using mechanically alloyed 93W-5.6Ni-l.4Fe powders showed tungsten particles of about 6-15 μm much finer
than those of 40 um in a conventional liquid phase sintered tungsten heavy alloy. An inhomogeneous distribution of the solid
solution matrix phase was obtained in the two-step sintered tungsten heavy alloy using partially mechanically alloyed powders.
The two-step sintered tungsten heavy alloy using mechanically alloyed 93W-5.6Ni-l.4Fe powders showed larger elongation of
16% than that of 1% in the solid state sintered tungsten heavy alloy due to the increase in matrix volume fraction and decrease
in W/W contiguity. Dynamic torsional tests of the two-step sintered tungsten heavy alloys showed reduced shear strain at maximum
shear stress than did the sintered tungsten heavy alloys using the conventional liquid phase sintering. |
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Keywords: | tungsten heavy alloy mechanical alloying two-step sintering microstructure mechanical properties |
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