Microstructure and mechanical properties of mechanically alloyed and solid-state sintered tungsten heavy alloys

Abstract

The mechanical properties of solid-state sintered 93W-5.6Ni-1.4Fe tungsten heavy alloys fabricated by mechanical alloying were investigated. Blended W, Ni and Fe powders were mechanically alloyed in a tumbler ball mill at a milling speed of 75 rpm employing a ball-to-powder ratio of 20:1 and a ball filling ratio of 15%. A nanocrystalline size of 16 nm and fine lamellar spacings of 0.2 mu m were obtained in mechanically alloyed powders at a steady state milling stage. Mechanically alloyed powders were consolidated into green compacts and solid-state sintered at 1300 degrees C for 1 h in a hydrogen atmosphere. The alloys sintered from mechanically alloyed powders showed fine tungsten particles (about 3 mu m in diameter) and a relative density above 99%. The volume fraction of the matrix phase was 11% and the tungsten/tungsten contiguity was determined to be 0.74. The alloys exhibited high yield strengths (about 1100 MPa) due to their fine microstructures, but exhibited reduced elongation and impact energy due to a large area fraction of tungsten/tungsten boundaries and the low volume fraction of matrix phase. (C) 2000 Elsevier Science S.A. All rights reserved.