Physical properties of wrought and cast copper alloys are listed in Tables 37A and 37B, respectively. From an engineering design standpoint, the most often sought physical properties are electrical and thermal conductivities, as is also the case with pure copper. Because these properties are based on electronic and lattice structures, both of which are affected by the presence of solute atoms, conductivity is strongly influenced by the presence of alloying (or impurity) elements. The effect varies widely with both element(s) in question and with their concentration. Metals such as silver, lead, cadmium, and zinc, for example, have a small influence at dilute concentrations ( 0.10 at. %), although their effect at high concentrations is larger. Other elements, notably phosphorus, silicon, arsenic, and tin, are more potent at all concentrations. The magnitude of the effect also depends strongly on the state of the alloying element, i.e., whether it exists in solid solution (strongest effect) or is present in a combined form, such as an oxide or intermetallic compound.
However, it is useful to point out that copper alloys are noteworthy for their many combinations of beneficial physical and mechanical (as well as chemical, e.g., corrosion) properties. Alloying generally serves to improve mechanical properties and often has a positive influence on corrosion behavior; thus the selection of a copper alloy for a given application often involves a reasonable compromise among the various properties required.
For example, zinc, tin, phosphorus, and beryllium degrade electrical conductivity while markedly increasing strength, yet brass (a copper–zinc alloy), phosphor bronzes (copper–tin– phosphorus), and beryllium coppers are widely used as electrical springs and connectors. Electrical conductivity in these alloys, while lower than that of pure copper, is nevertheless sufficiently high for the intended application, while the alloys’ high mechanical strength ensures the required degree of contact force.
COPPER AND COPPER ALLOYS
Konrad J. A. Kundig
Metallurgical Consultant
Tucson, Arizona
John G. Cowie
Copper Development Association
New York, New York
Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.
Edited by Myer Kutz
Copyright 2006 by John Wiley & Sons, Inc.
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