Enhanced strength–ductility synergy of carbon nanotube/Al–Cu–Mg composites via introducing laminate structure and grain modification

Laminate carbon nanotube (CNT)/Al–Cu–Mg composites consisting of alternate ductile layers (coarse or ultrafine grain Al) free of CNTs and brittle layers (ultrafine grain) rich in CNTs, were prepared in the powder metallurgy route. It was found that the strength-ductility of the composites was improved remarkably, as compared with those of uniform composites. Mechanical incompatibility between different layers during tensile deformation produced a large number of geometrically necessary dislocations (GNDs) between the ductile layers and the brittle layers, which inhibited the strain localization, thereby enhancing the strength-ductility. Compared with the laminate composite using the coarse grain Al as the ductile layers, the strength of the laminate composite using ultrafine grain Al as ductile layers further increased by 14%, while the elongation remained unchanged. This was because the ultrafine grain rather than coarse grain of the ductile layers could lead to higher strength and had better coordination with the brittle layers.