Pure unalloyed copper is soft and ductile, and usually contains approximately 0.7% impurities. Cadmium copper alloys are considered high copper alloys, they contain approximately 98 - 99 % copper, 0.1 - 1.5% cadmium and sometimes minor amounts of other materials. When cadmium is added to copper the material becomes more resistant to softening at elevated temperatures. The more cadmium that is added the more heat resistant the material becomes. Small additions of cadmium do not affect the thermal and electrical conductivities, and room temperature mechanical properties of cadmium copper. Cadmium copper is used in applications such as trolley wire, heating pads, electric blanket elements, spring contacts, connectors, and high strength transmission lines. Cadmium copper is used for trolley wire because it is extremely resistant to arc erosion. An extremely heat resistant cadmium oxide forms on the surface of the wire during arcing and protects it from eroding. This enables the cadmium copper wire to retain its strength under the high temperature conditions of the electric trains. It is also used for soldering applications, particularly to join components in automobile and truck radiators and semi conductor packaging operations. The uns alloy designations for cadmium copper alloys containing approximately 1% cadmium are c16200 and c16500. An alloy containing 0.1 to 0.2% cadmium is designated as c14300. There are no cast cadmium copper alloys.
The microstructure of the cadmium copper is similar to the pure copper materials. The alloying elements are in very low concentrations and they remain in solid solution with the alpha copper. The cadmium coppers are single phase alloys with the alpha copper structure. Cadmium copper is easily cold work and hot formed. Microstructures of the worked materials would contain equiaxed, twinned grains. The structures may contain oxide inclusions throughout the grains.