Interface Design Strategy for GNS/AZ91 Composites with Semi-Coherent Structure

The interfacial structure plays an important role in the mechanical properties of magnesium matrix composite (MMCs) reinforced with graphene nanosheet (GNS) due to their poor wettability with the Mg matrix. An interface design strategy was proposed to form the semi-coherent interfacial structure with superior bonding strength. The lattice mismatch and interfacial bonding strength between Mg/rare earth oxide/carbon were utilized as key characteristics to evaluate the interfacial structure. Lanthanum oxide (La2O3) was selected as the intermediate candidate due to its low lattice mismatch and high interfacial bonding strength. To identify the interfacial structure of Mg/La2O3/graphene, first-principles calculations were conducted to calculate the ideal work of separation and electronic structure of the interfaces. Results demonstrated the presence of strong ionic and covalent interactions at the interface, which theoretically verified the strong interfacial bonding strength among Mg/La2O3/graphene interfaces. To experimentally validate the interface strength, MMCs with the interface structure of Mg/La2O3/GNS were developed. The formation of in-situ La2O3 led to the successful attainment of semi-coherent structures between Mg/La2O3 and La2O3/GNS, resulting in high strength and good ductility of the composite. Overall, this work proposes a new approach to interface design in MMCs with an enhancement of mechanical properties.