Formation of ultra-fine copper grains in copper-clad aluminum wire

The microstructure formation at the interface in a copper-clad aluminum bimetallic wire has been investigated. Ultra-fine copper grains with sizes of 200 nm are formed near the Cu/Al interface when the wire is drawn after heat treatment. The formation of the ultra-fine copper grains is attributed to low-temperature recrystallization from strain that develops as the copper plastically flows around a broken dispersion of intermetallics at the interface. The ultra-fine copper grains added extra strength to the Cu/Al interface.