Microstructural control of and mechanical properties of mechanically alloyed tungsten heavy alloys

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~ for 1 hour in a hydrogen atmosphere. The solid state sintered tungsten heavy alloys were subsequently liquid phase sintered at 1445-1485~ 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 ktm much finer than those of 40 Bm 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.

Effects of Sintering Conditions on Structures and Properties of Sintered Tungsten Heavy Alloy

“…% usually supports brittleness of the final product [21]. On the other hand, increasing the addition of alloying, i.e., matrix-forming, elements generally decrease strength, but increase ductility [22]; high contents of matrix-forming elements contribute to uneven shape of the cross-section of the sintered piece due to gravity sedimentation during sintering, and consequently to non-uniformity of mechanical properties.…”

“…Under optimized sintering conditions, the W and NiCo phases are homogenously distributed and the sintered piece contains no visible pores [7]. Sintering is typically performed at temperatures between 1000 and 1500 • C to ensure melting of the matrix-forming binding elements [22,26,27]. The green sintered THA work pieces typically feature high density (16-18 g•cm −3 ), and relatively high strength and plasticity.…”

Effect of mechanical alloying process on microstructure and mechanical properties of ODS tungsten heavy alloys

“…In order to enhance the penetration performance of tungsten heavy alloy, several methods are proposed including W grain size control [10], alloying with Mo and Re [13], solid state sintering of mechanically alloyed powder [10,11], surface carburization [14], cyclic heat treatment [15] and oxide dispersion strengthening [11,12]. Among those methods, the oxide dispersion strengthening shows a change of dynamic fracture mode from adiabatic shear band to brittle fracture and is considered as improvement mechanism in penetration performance of tung- * Corresponding author.…”

“…Research to improve the penetration performance of tungsten heavy alloy have been carried out for replacement of depleted uranium, which has superior penetration performance with radioactive contamination problems [3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Effect of two-stage sintering process on microstructure and mechanical properties of ODS tungsten heavy alloy

“…Several studies have been carried out to enhance the mechanical properties of tungsten heavy alloy in order to improve the penetration performance for kinetic energy penetrator applications [3][4][5][6][7]21]. Recently, many investigators have studied the improvement of the mechanical properties by alloying with refractory elements such as Mo and Re [8,9], cold working followed by recrystallization [10], mechanical alloying [11][12][13][14][15][16][17] and oxide dispersion [16,17] in order to improve the mechanical properties.…”