Achieving ultra-high strengthening and toughening efficiency in carbon nanotubes/magnesium composites via constructing micro-nano layered structure

Magnesium (Mg) is the lightest metal structural material but exhibits low toughness. By imitating the structure of nacre, constructing micro-nano layered structure is an effective way to balance strength and toughness. The micro-nano layered structure is constructed by electrophoretic depositing carbon nanotubes (CNTs) on Mg foils. The CNTs layers embedded into 50 mu m Mg foils exhibit a strengthening efficiency of 500 while increasing the toughness of the composites. Experiments and theoretical calculation results reveal that the high back stress induced by CNTs layers is an important strengthening mechanism. The significantly improved toughness derives from the increase in energy required for crack propagation and high Schmid factor for the basal slip system {0 0 0 1} < 1 1 (2) over bar 0 >. This work provides a feasible and universal way for conductive matrix, such as aluminum, titanium, copper and even conductive polymers to construct micro-nano layered structure to break through the mismatch between strength and toughness.