Strength changes and bonded interface investigations in a spiral extruded aluminum/copper composite

• A near flawless interface was characterized in aluminum/copper composite rods.
• The interface was characterized using SEM/FIB and XRD techniques.
• Shear strength of the interface bond is higher than shear strength of pure aluminum.
• Micro-hardness distributions across the copper region agree well with EBSD results.
• EBSD results also proved a formation of ultra fine grains near the interface.

Fabrication of metal-based composites with concurrent grain refinement is an exciting and novel avenue in hybrid metal manufacturing. Copper clad aluminum rods, that were fabricated using Axi-Symmetric Forward Spiral Composite Extrusion (AFSCE) are investigated here as an example. Careful investigations of the bonding mechanism in the AFSCE samples are needed to control mechanical and physical properties of the composite material. In order to understand the mechanism of the bonding between copper and aluminum in the AFSCE process, morphological and micro-structural investigations were conducted by using a Scanning Electron Microscope/Focused Ion Beam (SEM/FIB) dual ion microscope and X-ray diffraction to study the nature of the interface. Hardness measurements across the interface region of the AFSCE sample were also produced to examine the deformation mechanism. A near flawless interface, without significant intermetallic or oxide layer, was identified. The strength variation in the copper region was characterized using micro-hardness tests which agreed well with the Electron Backscatter Diffraction (EBSD) observations of various sampling points. It was also found that the micro-hardness values near the interface and the outer periphery regions of the copper were higher than the hardness values at the middle region of the material, which is approximately equal to that of unprocessed copper.