Copper and copper alloys are some of the most versatile engineering materials available.
The combination of copper properties such as strength, conductivity, corrosion resistance, machinability and ductility make copper suitable for a wide range of applications.
These copper properties can be further enhanced with variations in composition and manufacturing methods.
- Electrical conductivity: Copper has the highest conductivity of the engineering metals. Silver or other elements may be added to increase strength, softening resistance or other properties without major loss of conductivity.
- Thermal conductivity: This property is similar to electrical conductivity. Alloys of copper may be used for this property, where good corrosion resistance compensates for loss of conductivity with increased alloying.
- Color and appearance: Many of the copper alloys have a distinctive color, which may change as the object weathers. For most alloys, it is easy to prepare and maintain the surface standard, even in adverse corrosion conditions. Many of the alloys are used in decorative applications, either in their native form or after metal plating. The alloys have specific colors, ranging from the salmon pink of copper through yellow, gold and green to dark bronze in a weathered condition. Atmospheric exposure can produce a green or bronze surface, and pre-patinated alloys are available in some product forms.
- Corrosion resistance: All copper alloys resist corrosion by fresh water and steam. In most rural, marine and industrial atmospheres, copper alloys are also resistant to corrosion. Copper is resistant to saline solutions, soils, non-oxidizing minerals, organic acids and caustic solutions. Most ammonia, halogens, sulfides, solutions containing ammonia ions and oxidizing acids, like nitric acid, will attack copper. Copper alloys also have poor resistance to inorganic acids. The corrosion resistance of copper alloys comes from the formation of adherent films on the material surface. These films are relatively impervious to corrosion therefore protecting the base metal from further attack.
- Ductility can be restored by annealing: This can be done either by a specific annealing process or by incidental annealing through welding or brazing procedures.
- Hardening/Strengthening: There are four common ways to harden (strengthen) copper such as strain hardening, solid-solution hardening, precipitation hardening and dispersion strengthening. The fifth, spinodal decomposition, is currently used commercially, but only in certain copper-nickel-tin alloys. Combinations of strengthening mechanisms are often used to provide higher mechanical properties in high-copper alloys.
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