Microstructure and mechanical behaviors of Al/Cu laminated composites fabricated by accumulative roll bonding and intermediate annealing

Strength and toughness of laminated composites with alternatively stacked “brick-and-mortar” structure can be synchronously improved along the direction parallel to the layer interface. However, it is still a challenge to prepare high-performance laminated composites in large quantities to meet industrial needs. In this work, we employ accumulative roll bonding (ARB) and/or intermediate annealing to prepare Al/Cu laminated composites as cheaper substitutes for Cu alloys due to lightweight and considered electrical conductivity. Our results show that the ARB process decreases the layer thicknesses and grain sizes, and improves the Vickers micro-hardness of Al/Cu laminated composites. As the ARB cycle increases from 1 to 8, the tensile strength firstly increases from 279.20 MPa to 358.71 MPa, and then decreases to 317.88 MPa. Meanwhile, the uniform elongation firstly increases from 1.25% to 1.71%, and then decreases to 0.58%. These variations of tensile properties are tightly linked to the layer-integrity and microstructures of Al and Cu layers. Moreover, the intermediate annealing (350 °C for 30 min) applied after every 2 ARB cycles can significantly increase the tensile strength, uniform elongation and elongation to failure, especially for Al/Cu laminated composites with high ARB cycles, because intermediate annealing remarkably improves the interfacial metallurgical bonding and continuity/integrity of Al and Cu layers. However, the final annealing for long time would introduce brittle intermetallics (like AlCu and Al2Cu), and therefore deteriorate the tensile ductility. This work provides a new treatment process for fabricating Al/Cu laminated composites with synchronously increasing strength and ductility.