Introduction and Application of Tungsten Heavy Alloys II

Tungsten heavy alloys generally are refractory metal, which have two-phase composites consisting of W-Ni- Fe or W-Ni- Cu or even W-Ni-Cu-Fe, some tungsten alloy is added Co、Mo、Cr, etc. They have very high melting point and have a density twice that of steel and are more than 50% heavier than lead. Tungsten content in conventional heavy alloys varies from 90 to 98 weight percent and is the reason for their high density (between 16.5 and 18.75 g/cc).

Nickel, iron and copper serve as a binder matrix, which holds the brittle tungsten grains together and which makes the alloys ductile and easy to machine. Nickel-iron is the most popular additive, in a ratio of 7Ni:3Fe or 8Ni:2Fe (weight ratio). The conventional processing route for tungsten heavy alloys includes mixing the desired amount of elemental powders, followed by cold pressing and liquid phase sintering to almost full density. The matrix alloy melts and takes some tungsten into solution during liquid phase processing, resulting in a microstructure through which large tungsten grains (20–60µm) are dispersed in the matrix alloy.

The as-sintered material often is subjected to thermo mechanical processing by swaging and aging, which results in increased strength and hardness in the tungsten heavy alloys.


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