Behavior of Al-Al2O3 metal/ceramic multilayers under indentation and shock loadings

Abstract

Multilayers made of soft metallic and hard ceramic layers exhibit higher strength and toughness. Here we demonstrate a significantly high hardness when the individual layer thickness is well below 100nm. Nanoindentation measurements show significantly greater, 13-fold, enhancement of hardness with the decrease in layered thickness. A deviation from Hall-Petch relationship was observed as the layer thickness decreases to 10 nm, suggesting grain boundary sliding mechanism would be operative. We demonstrate the multilayered structures absorb more energy under shock deformation than the nonlayered structures with similar areal densities, making the layered structures more efficient than their bulk counterparts.