Effect of the incorporation of graphene reinforcement layers on the microstructure and mechanical properties of AX20 laminated composites processed by accumulative roll bonding

To address the limitations and deficiencies of traditional processing technologies, this study achieves the uniform dispersion of graphene nanoplatelets (GNPs) in AX20 magnesium alloy via an innovative electrophoretic deposition (EPD)-accumulative roll bonding (ARB) hybrid process. By synergizing the strengthening effect of GNPs and the microstructure regulation advantage of multi-pass severe plastic deformation (SPD), this work systematically clarifies the interfacial evolution law, grain refinement mechanism, and deformation coordination strengthening mechanism of the composite during ARB processing. Key findings demonstrate that the two-pass GNPs-reinforced composite (ARB-G2) forms a lamellar bimodal microstructure characterized by the coexistence of coarse subgrains and fine dynamically recrystallized grains. Its yield strength reaches 253.19 MPa, which is 20.41% higher than that of the two-pass pure AX20 alloy (ARB-2), while maintaining relatively stable ductility compared to the single-pass GNPs-reinforced sample (ARB-G1). This strength-ductility synergy originates from three core mechanisms: First, GNPs induce grain refinement via the particle-stimulated nucleation (PSN) effect and inhibit grain coarsening. Meanwhile, multi-pass ARB further increases the dislocation density and optimizes the dispersion of GNPs, alleviating the deformation incompatibility between the matrix and the reinforcement. Furthermore, the efficient activation of the pyramidal <c+a> slip system provides additional deformation degrees of freedom. This study offers a feasible technical route for the controllable preparation of high-performance lightweight magnesium matrix composites.