What is tungsten?

Tungsten, from the Swedish tung sten meaning ‘heavy stone'; chemical symbol W, was first isolated in 1783. The heavy alloys of this hard, dense metal should not be confused with tungsten carbide, as used in cutting tools. These alloys typically contain 90 - 97 wt%, hence deriving their fundamental properties from tungsten. As a result, WHAs are becoming the materials of choice for designers and engineers who require such properties as high density, good mechanical strength and ease of machining for use in radiation shielding and collimation and above all, counterweights and ballast.

Therefore, tungsten added with Ni, Fe, Cu is very suitable matreial for counterweights. You could visit tungsten-alloy.com. for more details.