Defects in graphene nanoplatelets and their interface behavior to reinforce magnesium alloys

Defects in graphene nanoplatelets (GNPs) and their interface behavior to reinforce magnesium alloys was studied by using two types of GNPs, one with high integrity and the other with multiple defects, as reinforcements in ZK60 alloy. Herein, GNPs prepared by chemical exfoliation exhibited multiple defects, such as carbon atom vacancies, dangling carbon bonds, oxygen-containing functional groups and wrinkles. During the composite fabrication, Mg atoms restored the sp(2) structure of graphene and reacted with the oxygen-containing groups on graphene, leading to a strong interfacial bonding. Meanwhile, graphene defects scattering in nanoscale triggered nucleation of Mg nanograins, which connect the hard GNPs and soft Mg matrix for effective transfer of stress and strain. The defective GNPs (0.05 wt%) reinforced ZK60 alloy with large tensile yield strength enhancement (65%) and especially remarkable elongation improvement (44%). This work highlights the structural feature of GNPs to reach their full strengthening potential as reinforcements in metal matrix composites.