Termination of local strain concentration led to better tensile ductility in multilayered 2N/4N Al sheet

Multilayered aluminum composites (ARB6-2N/4 N) with alternating layers of commercially purity aluminum (2N–Al) and high-purity aluminum (4N–Al) were fabricated by six cycles of accumulative roll bonding (ARB) processing. The ARB processed specimens were annealed at different temperatures. It was found that heterogeneous lamellar microstructures composed of fine-grained 2 N (hard) layers and coarse-grained 4 N (soft) layers formed in the specimens. The specimen with the heterogeneous layered structure showed a large tensile elongation with a strength following the rule of mixture. Digital image correlation analyses revealed that the deformation bands with high local strains formed in the 4 N layers but were terminated at the interfaces between the 2 N and the 4 N layers in the multilayered aluminum composites, accommodating the deformation between the hard (2 N) layers and the soft (4 N) layers during tensile deformation. Termination of the strain localization delayed macroscopic necking of the materials, leading to a better combination of high strength and good ductility in the multilayered aluminum composites.