Microstructure and properties of ultra-fine tungsten heavy alloys prepared by mechanical alloying and electric current activated sintering

The microstructure and properties of the 93W-4Ni-2Co-1Fe (mass fraction, %) tungsten heavy alloys prepared by mechanical alloying and electric current activated sintering from mixed elemental powders were investigated. After 15 h milling, the average W grain size in the powders is decreased to 120 nm. For the powders milled for 15 h, the density, hardness and transverse rupture strength of the alloys sintered only by an intensive pulse electric current are the maximum. When the total sintering time keeps constant, the properties of the sintered alloys can be obviously improved by optimizing the sintering time of pulse- and constant-currents. A bulk ultrafine alloy with an average W grain size of about 340 nm can be obtained by sintering 15 h-milled powders in a total sintering time of 6 min. The corresponding sintered density, hardness and transverse rupture strength reach 16.78 g/cm3, HRA84.3 and 968 MPa, respectively.