Physical properties of pure copper and copper alloys are quite similar in terms of the melting point, the density, the Young’s modulus, and the thermal expan­sion coefficient. Table 1 compares the room tem­perature physical properties of pure copper, PH CuCrZr, and DS CuAl25.2,27-29 Because PH copper alloys and DS copper alloys contain only a small amount of fine second-phase particles, the physical properties of these copper alloys closely resemble those of pure copper.

The conductivity of copper and copper alloys is the most important physical property for their applications. The electrical conductivity of copper can be reduced by thermal vibration of atoms and crystal imperfections, for example, solute atoms, vacancies, dislocations, and grain boundaries. These different mechanisms have additive contributions to the increase in resistivity. As with other metals, the thermal conductivity of copper, kth, is proportional to the electrical conductivity, l, described by the Wiedemann-Franz law, that is,

kth = 1LT [1]

where T is the absolute temperature and L is the Lorentz number. The electrical conductivity of pure copper is sensitive to temperature, and less sensitive to the amount of cold work and the grain size. The linear temperature coefficient for electrical

resistivity in copper is dp/dT = 6.7×10-11 OmK-1.30 Severe cold work can reduce the electrical conductiv­ity of copper by only 2-3% IACS.

All alloying elements in copper reduce the elec­trical conductivity, and the amount of degradation depends on the type of element, the concentration, and microstructural form (e. g., solid solution, pre­cipitation, or dispersion). Figure 2 compares the strength and conductivity of copper and several types of copper alloys.31