Improvement of mechanical and electrical properties of rotary swaged Al-Cu clad composites

Abstract

With the aim to investigate modifications in electric resistivity, mechanical properties and structures of Al/Cu clad composites induced by various thermomechanical treatments, Al/Cu work-pieces were swaged under two temperatures to three final diameters and subsequently subjected to two different heat treatments. The influence of the two swaging temperatures on formability of the composites was evaluated via tensile and bending tests with integrated acoustic emission detection. The highest tensile strength (-500 MPa) was recorded after the semi-final swaging pass for both of the composites. The strain imposed during the gradual swaging process significantly influenced hardness of both of the metals in the composites, the development of which was non-linear. Structure analyses confirmed restoration processes in Cu to occur during swaging to 5 mm at 25 degrees C, however, at 250 degrees C the restoration occurred during the last but one pass to 7.5 mm already. The structural changes also induced simultaneous texture modifications. The heat treatment introduced further structure changes; the 350 degrees C annealing temperature resulted in the development of an intermetallic layer on the Al/Cu interfaces, which also contributed to decreases in mechanical properties. The results of electric resistivity measurements showed all the composites to have higher conductivity than Al work-pieces swaged using the identical procedures.