Decipher the ultra-high strengthening and toughening efficiency of GNS-MgO/Mg layered composite with in-situ enhanced interface

Abstract

Constructing graphene/metal layered structure serves as a promising way to solve the strength-toughness trade-off of metallic materials, while the weak interlayer interfaces usually lead to premature failure of the composites. This work focuses on the interfaces of the GNS-MgO/Mg layered composite with ultra-high strengthening and toughening efficiency. The yield strength and elongation were increased by 137% and 16.5%, with impressively 0.13 wt% GNS-MgO nano layers. Interface analysis based on atomistic simulations, interface observation, fractography, and AFM observation clarify the crucial role of MgO films and thinner GNSs in delaying crack initiation. Statistics based on EBSD and in-house codes, TEM observation, and atomistic simulations demonstrate the effect of GNS-MgO layers on higher density of geometry necessary dislocations (GNDs) and statistical storage dislocations (SSDs). Additional back stress hardening induced by GNDs and SSDs provides the GNS-MgO/Mg composite with ultra-high strengthening efficiency. This study provides comprehensive insights into the interfacial design and the effects of interface strength on mechanical properties of layered composites. The proposed preparation method could be extended to other graphene/metal systems.