Development of a new W-Ni-Mn heavy alloy. (Reannouncement with new availability information)

Tungsten heavy alloys are two-phase composites consisting of nearly pure grains of tungsten dispersed in a ductile matrix of tungsten, nickel, and iron/copper/cobalt. They are processed from elemental powder mixes (tungsten content between 90 to 98 weight percent) by classic liquid-phase sintering. The typical liquid-phase sintering temperature for classic tungsten heavy alloys varies from 1450 to 1500 deg C. This temperature range is too high for general powder metallurgical production furnaces. The Ni-Mn phase diagram predicts that lower liquid-phase sintering temperatures are possible for tungsten heavy alloys if nickel and manganese are used as the binder phase. This paper describes the preliminary investigations in the development efforts for producing W-Ni-Mn based heavy alloy with 90 weight percent tungsten. The material can be sintered to high densities (90% or more of theoretical) at temperatures in the range of 1200 to 1300 deg C. The results indicate that oxide contamination and residual porosity are the major problems in sintering of these heavy alloys. The tensile properties of the alloy are extremely poor which is expected due to the level of retained porosity in the material.