Flake thickness effect of Al_2O_3/Al biomimetic nanolaminated composites fabricated by flake powder metallurgy

摘要

Al_2O_3/Al biomimetic nanolaminated composites were fabricated by means of a flake powder metallurgy approach, in which pure Al flake powders with native Al_2O_3 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 Al_2O_3 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 Al_2O_3/Al nanolaminated composites, a FAPT of ～500 nm is suggested for maximum toughness and smaller for higher tensile strength.