Aluminum alloys, density, thermal conductivity

Aluminum metal and, to a lesser extent, aluminum alloys are suitable materials for manufacturing industrial cathodes. Actually, pure aluminum metal exhibits a low density (2690 kg.m" ) and high thermal conductivity (237 Wm K ), is a good electrical conductor (2.6548 p 2.cm), does not form hydride with nascent hydrogen, and passivates when polarized anodicaUy. All these characteristics, along with a reasonable average cost of 2.734 US /kg (for 99.7 wt.% Al), are major assets for its wide utilization especially in zinc electrowinning. 

The in-plane thermal conductivity of quasi-isotropic laminates reinforced with UHM pitch carbon fibers is similar to that of aluminum alloys, while UHK pitch carbon fibers provide laminates with a conductivity over 50 percent higher. Both materials have densities about 35 percent lower than aluminum. 

Aluminum and its alloys are characterized by a relatively low density (2.7 g/cm as compared to 7.9 g/cm for steel), high electrical and thermal conductivities, and a resistance to corrosion in some common environments, including the ambient atmosphere. Many of these alloys are easily formed by virtue of high ductility this is evidenced by the thin aluminum foil sheet into which the relatively pure material may be rolled. Because aluminum has an FCC crystal structure, its ductility is retained even at very low temperatures. The chief limitation of aluminum is its low melting temperature [660°C (1220°F)], which restricts the maximum temperature at which it can be used. 

Physical Proporlios. Table 7 lists densities, melting points, thermal conductivities, and electrical conductivities for selected wrought aluminum alloys. 

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