High-ductility aluminium alloys including small sub-grains with wide low angle boundary

Strongly interacting interfaces with other constituents in materials lead to outstanding performance beyond their inherent properties. It is closely related with the interfacial structure, generally determined by interfacial chemistry based on thermodynamics. Here, we introduce a new strategy for tailoring high-ductility aluminium alloys by developing small sub-grains induced by the wide low-angle boundary (WLAB). The WLAB is developed by the formation of the band in which oxygen atoms are interstitially located in the aluminium (called as I-Al). The band with ∼40 nm in width, which has a coherent chemical interface with a very small misfit strain, is individually dispersed in the matrix, producing the WLAB, thereby partitioning whole grains into numerous sub-grains (<1 µm). Further structural information investigated by neutron total scattering techniques supports the presence of interstitial oxygen by unveiling local structure of the WLAB and slight lattice expansion in the I-Al. During plastic deformation, the WLAB which contains pre-existing dislocations promotes dislocation interactions as the way of the formation of dislocation cells. The consequent dislocation storage capacity with very small dislocation cells the size of which is far below a critical size observed in conventional aluminium alloys renders significantly a large ductility without sacrificing tensile strength.