Heavy metal alloys are pseudo-alloys of tungsten with a nickel-iron or nickel-copper matrix. They are produced by powder metal and sintering processes. Tungsten Heavy Alloys has a high density of 17-19 g/cm³. Comparable densities are only reached by gold or platinum. These alloys are used as mass balancing weights and attenuators in aircraft construction, in motors and power trains, as oscillating weights and centrifugal weights in machines and in equipment construction, and in medical technology for both protection from and focusing of ionizing radiation in x-ray and measuring devices.