Abstract: Graphene nanoplatelets/Mg-14Li-1Al (GNPs/LA141) composites sheets with a micro-nano laminated structure were fabricated using electrophoretic deposition (EPD) combined with accumulative roll bonding (ARB), achieving a synergistic enhancement of strength and ductility. The interfacial relationship between GNPs and the matrix, mechanical properties, fracture behavior, and strengthening mechanisms of the micro-nano laminated composites were investigated. The results show that the thickness of GNPs at the interface decreases with the increase of ARB cycles. The nano-laminated GNPs-LA141 bonding between the GNPs and the LA141 matrix enhances the interfacial bonding strength. The strong interfacial bonding is an effective factor in enhancing the mechanical properties of GNPs/LA141 composites. Strong interface bonding effectively enhances load transfer strengthening, and high modulus GNPs produces high back stress hardening. Simultaneously, GNPs promotes dynamic recrystallization (DRX) nucleation and restricts grain growth, thus facilitating the grain refinement and enhancing the strength of the composite. The increase in ductility is attributed that graphene increases the resistance of crack propagation and the lamellar structure causes the crack propagation path lengthening during the fracture process. The GNPs/LA141 composite sheet exhibits a yield strength of 221 MPa and an elongation of 20.5 %, which is 81.1 % and 66.7 % higher than the as-cast alloy, respectively. This work successfully produced GNPs/LA141 composite sheets with high strength and high plasticity, while also provided a new approach and theoretical basis for preparing Mg-Li based composites, of which the matrix has a high chemical activity.

Key words: LA141, Graphene nanoplatelets, Accumulative roll bonding, Metal matrix composites, Strength-plasticity mechanism