INFLUENCE OF PRE-ALLOYED NI-FE-MO BINDER METAL ON PROPERTIES AND MICROSTRUCTURE OF TUNGSTEN HEAVY ALLOYS

The effect of a pre-alloyed Ni-Fe-Mo binder metal on the properties an d microstructure of tungsten heavy alloys has been investigated. The r esults show that the 93W + 7 (Ni-Fe-Mo) heavy alloy in which the pre-a lloyed Ni-Fe-Mo powder was used for binder metal has a higher tensile strength and a better ductility than the 93W + 4.9Ni + 2.1Fe heavy all oy. Because of the very fast diffusion of molybdenum in tungsten, the molybdenum is well distributed in tungsten grains and matrix in the 93 W + 7 (Ni-Fe-Mo) alloy after sintering, though molybdenum has been pre -alloyed in the binder metal before sintering. The tungsten content in the matrix of the 93W + 7 (Ni-Fe-Mo) alloy is clearly reduced. Howeve r, the growth of tungsten grains during sintering was not found to be restrained. The pre-alloyed Ni-Fe-Mo binder metal makes the 93W + 7(Ni -Fe-Mo) alloy have a liquid of higher molybdenum content in the initia l stage of sintering, which may be favourable for reducing the interfa cial energy of tungsten (solid)-matrix (liquid) and for obtaining a lo wer contiguity.