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

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 m illing 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 spa cings of 0.2 mu m were obtained in mechanically alloyed powders at a steady state milling stage. Mechanically alloyed powders were consolidated into g reen compacts and solid-state sintered at 1300 degrees C for 1 h in a hydro gen atmosphere. The alloys sintered from mechanically alloyed powders showe d 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 tungste n/tungsten contiguity was determined to be 0.74. The alloys exhibited high yield strengths (about 1100 MPa) due to their fine microstructures, but exh ibited 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.