Preparation And Microstructure Properties Of Reduced Graphene Oxide Reinforced Magnesium Matrix Composites

Graphene oxide has good surface activity and has excellent mechanical properties of graphene,so graphene oxide is one of the ideal reinforcements of metal matrix composite materials.Graphene oxide has a unique two-dimensional structure,which can provide a larger load transfer interface in the composite material,but a larger specific surface area is likely to cause self-aggregation of the reinforcement,causing the interface strength in the metal matrix composite material to be greatly weakened,which is easy to become crack source.In order to avoid the self-agglomeration of the reinforcement and improve the interfacial bonding strength of the composite material,the graphene oxide was used as the raw material to prepare the Al surface-modified reduced graphene oxide(Al@RGO),which was evaluated by XRD,XPS and infrared spectroscopy.The state of various elements and the presence of functional groups before and after surface treatment are described to explain the surface modification mechanism.Al@RGO is added to the magnesium matrix by semi-powder metallurgy,and characterize and analyze the microstructure,mechanical properties and interface of the composite material,and explore the effect of the reinforcement on the composite material;The strengthening mechanism is calculated and characterized to provide theoretical guidance for the research of magnesium-based composite materials.The results are as follows:The research on the surface modification process of graphene oxide shows that the optimal concentration of graphene oxide ultrasonic dispersion for surface modification is 0.3 mg/ml,and the optimal solution value for surface modification is 0.8.The surface modification in absolute ethanol medium is mainly carried out by surface complexation,and as the p H value of the adsorption solution increases,the ion exchange effect is enhanced.When the p H value reaches 0.8,the upward trend of ion exchange effect will weaken.For the heat treatment process of Al@GO,due to the low thermal reduction temperature,most of the Al element still exists in the form of complex aluminum and Al-O,and a small part is converted into amorphous Al₂O₃.The surface potential of Al@RGO repels,inhibiting the self-aggregation between the sheets and facilitating their redispersion in ethanol.The content of reinforcement in Al@RGO/Mg and Al@RGO/AZ91 composites is limited by the preparation process,and the maximum addition amount is 1.0 wt.%;Al@RGO is added to matrix,the Al and O elements on the surface will react with the pure Mg matrix to generate Mg₁₇Al₁₂ The phase relationship between Mg O,Mg₁₇Al₁₂and?-Mg is:[123]_Mg17Al12?[-24-23]?_-Mg and(-22-2)_Mg17Al12?(-1010)?_-Mg,the phase relationship between Mg O and?-Mg is:[011]_{Mg O}?[-24-23]?_-Mg and(-11-1)_{Mg O}?(0-1-1-2)?_-Mg,and the dislocations and lattices between Al@RGO,?-Mg and the interface mismatch are watched.In the extrusion process,0.1 wt.%Al@RGO promotes the continuous dynamic recrystallization of the matrix,and when Al@RGO reaches 0.5 wt.%,the reinforcement will accelerate the generation of dynamic recrystallization of the matrix,and the dynamic recrystallization grains will continue to grow.The second phase precipitated during the extrusion process of Al@RGO/AZ91 composites will also enhance the promotion of Al@RGO on dynamic recrystallization.When the Al@RGO in the composite is 0.1 wt.%,the dynamic recrystallization of Al@RGO/AZ91composites is more obvious than Al@RGO/Mg composites.When the Al@RGO in the composite is0.5 wt.%And 1.0 wt.%,the dynamic recrystallization grains of the composite will grow further.Research on strengthening mechanism shows that when the amount of Al@RGO added is 0.1 wt.%,the reinforcement can effectively refine the grain.When content of Al@RGO reachs 0.5 wt.%and 1.0 wt.%,the dynamic recrystallization grains in the composite will grow,weakening the effect of fine grain strengthening,and the contribution of load transfer strengthening to the yield strength will increase with the increase of the reinforcement content.As the content of Al@RGO increases,the thermal mismatch strengthening effect will gradually increase.Affected by the dispersion effect of the reinforcement,the Orowan strengthening effect will show a trend of increasing first and then decreasing.