Microstructural Control of and Mechanical Properties ofMechanically Alloyed Tungsten Heavy Alloys

摘要

93W-5.6Ni-l.4Fe tungsten heavy alloys withcontrolled microstructures were fabricated by mechanically alloy-ing of elemental powders of tungsten, nickel and iron by twodifferent process routes. One was the full mechanical alloying ofblended powders with a composition of 93W-5.6Ni-l.4Fe, and theother was the partial mechanical alloying of blended powders witha composition of 30W-56Ni-l4Fe followed by blending withtungsten powders to form a final composition of 93W-5.6Ni-l.4Fe.The raw powders were consolidated by die compaction followedby solid state sintering at 1300℃ for 1 hour in a hydrogenatmosphere. The solid state sintered tungsten heavy alloys weresubsequently liquid phase sintered at l445~l485℃ for 4~90 min.The two-step sintered tungsten heavy alloy using mechanicallyalloyed 93W-5.6Ni-l.4Fe powders showed tungsten particles ofabout 6~l5 μm much finer than those of 40 μm in a conventionalliquid phase sintered tungsten heavy alloy. An inhomogeneousdistribution of the solid solution matrix phase was obtained in thetwo-step sintered tungsten heavy alloy using partially mechanicallyalloyed powders. The two-step sintered tungsten heavy alloy usingmechanically alloyed 93W-5.6Ni-l .4Fe powders showed largerelongation of 16% than that of 1% in the solid state sinteredtungsten heavy alloy due to the increase in matrix volume fractionand decrease in WIW contiguity. Dynamic torsional tests of thetwo-step sintered tungsten heavy alloys showed reduced shearstrain at maximum shear stress than did the sintered tungsten heavyalloys using the conventional liquid phase sintering.