Interfacial bonding mechanism of graphene nanoplatelets reinforced AZ91D magnesium alloy prepared by semi-solid injection molding

Abstract

The incompatibility between the strength and thermal conductivity of magnesium alloys limits their application in heat dissipation components. Magnesium matrix composites were obtained by adding reinforcements into the AZ91D alloy to achieve synergistic enhancement of mechanical and thermal conductivity to promote the application of magnesium alloy. Graphene nanoplatelets (GNPs) reinforced magnesium matrix composites were successfully prepared by semi-solid injection molding. The high viscosity of the semi-solid metal slurry contributes to the homogeneous dispersion of GNPs in the magnesium matrix. A GNPs/MgO/Mg heterostructure with high interfacial bonding strength was found at the interface of GNPs and α-Mg matrix. The semi-solid casting method improves the mechanical properties of the composites by grain refinement and simultaneously reduces the thermal conductivity. The addition of GNPs can balance the mechanical and thermal conductivity enhancement, and the most balanced properties of the composites are obtained when the content of GNPs is 0.3wt.%, with a tensile strength of 243.1MPa, Vickers hardness of 93.7 HV, and thermal conductivity of 74.8W/(m·K). Therefore, the semi-solid forming method is considered a promising processing method, and GNPs is considered an ideal reinforcement material to improve the performance of the magnesium matrix.