Processing of lightweight Cu-intermetallic-Al composite through cyclic accumulative roll bonding and intermediate annealing

In the present research, the effects of cyclic accumulative roll bonding and intermediate annealing on the microstructural evolution, intermetallic compounds formation and mechanical properties of lightweight Cu-Al multi layered composites were investigated. Commercially pure copper and aluminum 1050 sheets were used to prepare initial sandwich which was then underwent as many as five ARB cycles, with an intermediate annealing treatment at 450°C for one hour. Comprehensive microstructural analysis using optical microscopy, scanning electron microscopy, and X-ray diffraction were done. Results show that during intermediate annealing significant grain refinement in Cu and Al layers were occurred and the gradual development of intermetallic compounds, particularly Al 2 Cu, AlCu, and Al 4 Cu 9 , at the Cu/Al interfaces were formed. During the intermediate annealing, after each ARB pass, intermetallic compounds form continuous bands between the copper and aluminum layers, and then during each subsequent ARB pass after intermediate annealing, those banded compounds break and distributed in the matrix. In this manner, a homogeneous Cu/Intermetallic/Al composite is obtained. Also, it is seen that with increasing of ARB passes and intermediate annealing times, the volume fraction of brittle intermetallic compounds increased and their morphology changed from continuous layered to homogeneous fragmented and distributed form. The mechanical properties of the processed Cu/Intermetallic/Al composite are largely dependent on the morphology and volume fraction of the intermetallic compounds. When the intermetallic compounds are present in a fragmented form at the interface between the layers or distributed in copper matrix (as occurred after 4 ARB passes), the ductility is greatly reduced due to the increase in stress concentration regions around the intermetallic particles.