What is the Evolution of Copper Cadmium and Copper Chromium Zirconium Alloys

What is the Evolution of Copper Cadmium and Copper Chromium Zirconium Alloys

Silver - Cadmium: In the 1970s cadmium was added to silver to make electrical contact alloys. Cadmium added to silver contacts minimizes or prevents arcing by extinguishing the arc to give longer life to contacts that are switching currents frequently.

Copper - Cadmium:  Moving forward, in the 1980s copper cadmium alloy set the standard for high strength copper alloy conductors. The designation of copper cadmium or UNS C16200 (rod, bar, wire) is an amazing alloy where as little as 0.7 % of cadmium added to copper can double the ultimate strength of copper while minimally affecting electrical conductivity. This higher strength improves flexing properties of copper conductors so they can be used in applications where the wire is not fixed, and regular copper wire would break do to localized work hardening. C16200 was marketed as wire and rod in demanding applications, i.e. tinsel wire for phone cords (remember those curly cords before wireless), overhead conductors for electric trains, electric blanket conductors, signal wire for oil exploration, torpedo guide wires for submarine and helicopter launched torpedoes, braided speaker wires, ABS auto signal wires, and lots of other electronics where wires needed better flexibility and rods required higher strength with good or great electrical conductivity.

Copper - Zirconium: In the mid-20th century, The American Metal Climax Company (AMAX) developed a copper zirconium alloy. This alloy with a small addition of zirconium to oxygen-free copper increases the softening resistance at high temperatures with an improvement in high-temperature properties over traditional silver-bearing copper alloys. Copper zirconium or UNS C15000, has replaced cadmium copper or C16200 as a Class 1 resistance electrode material. Zirconium Copper UNS C15000 remains an important alloy today in resistance welding as well as power generation and aerospace applications.

Copper - Cadmium - Chromium: Another variation, developed approximately 50 years ago, is a combination of copper + cadmium+ chromium which was created at Phelps Dodge Specialty Copper Products in Elizabeth, NJ. This alloy called PD135 or C18135 replaced a portion of the cadmium with chromium, offering a strengthened via precipitation hardening in addition to the work hardening component of copper-cadmium. This alloy became one of the premier conductor choices for airframes for decades adding another layer of reliability in an industry sector that always demands the best in quality and performance.

Copper - Chromium - Zirconium alloys are now replacing Copper-Cadmium and Copper - Cadmium - Chromium as cadmium has been identified as a carcinogen and has been placed on the RoHS list. Due to the toxicity of Cadmium and its compounds the use of this metal is diminishing and resulting in replacement materials. The best replacement is C15000 and C18150 or other copper + chromium +zirconium alloys with similar properties depending on the application.  

By Tom Chandler, Metallurgist Engineer, Cadi Company