Flake thickness effect of Al2O3/Al biomimetic nanolaminated composites fabricated by flake powder metallurgy

Al2O3/Al biomimetic nanolaminated composites were fabricated by means of a flake powder metallurgy approach, in which pure Al flake powders with native Al2O3 nano-skins were assembled into a biomimetic nanolaminated structure. The tensile properties of the composites were investigated experimentally and numerically, and a flake thickness effect was revealed. It was found that the tensile strength increased monotonously with decreasing flake Al powder thickness (FAPT) and reached a maximum of ~435 MPa at a FAPT of ~180 nm. At a FAPT of ~500 nm, a well-balanced strength and ductility was achieved, resulting in a maximum work-of-fracture. Both the decrease in grain size of Al matrix and the increase in volume fraction of Al2O3 contribute to the increase in tensile strength caused by decreasing FAPT. At FAPTs greater than 500 nm, the former is dominant; at FAPTs less than 500 nm, the latter is dominant. For Al2O3/Al nanolaminated composites, a FAPT of ~500 nm is suggested for maximum toughness and smaller for higher tensile strength.