Copper-nickel alloys, free of patinas, have a unique, aesthetically pleasing range of colors. The color becomes lighter as nickel is added. Low-nickel alloys cast a yellow-pink hue. Alloys containing 15-30% nickel and above have a silvery-white appearance similar to stainless steel and are used in coinage. In seawater, the alloys can turn various colors including golden brown, dark brown or green, depending on the iron content, immersion time and seawater conditions.
The physical properties of copper-nickel alloys vary according to composition. Melting range temperatures, electrical resistivity and modulus of elasticity increase with nickel content. However, thermal conductivity decreases as the percent of nickel increases.
Typical physical properties of copper-nickel alloys are illustrated below.
|Specific Heat||J/kg °K||377||377||377|
|Coeff. of Linear Expansion
|Electrical Resistivity||microhm. cm||19||34||50|
|Modulus of Elasticity||GPa||135||152||156|
|Modulus of Rigidity||GPa||50||56|
Thermal conductivity and expansion characteristics are of particular interest for heat exchangers and condensers.
Low magnetic permeability is required in some applications, such as minesweepers. Although 70-30 Cu-Ni is essentially non-magnetic, 90-10 Cu-Ni has a higher iron content. Its permeability can be between 1.01 and in excess of 1.2, depending on final heat treatment conditions. A fast cool from the final solution heat-treatment temperature is required to achieve low permeability.
- The Behaviour of CuNi 90/10 vs 6Mo Superaustenitic and Superduplex Steels in Marine Environments, Jasner, M., Hecht, M., and Beckmann, W., , Osnabruck, KME Europa Metal Aktiengesellschaft, .