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| Molecular Dynamics Study of the Effect of Graphene on the Compressive Properties of Magnesium Matrix Composites |
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Abstract Magnesium (Mg), a lightweight metal material, is constrained in its applications due to its poor plasticity and low strength at high temperatures. Graphene (Gr) has the characteristics of large specific surface area and high strength. It is an ideal reinforcement for improving the mechanical properties of materials. Molecular dynamics (MD) simulation was employed to investigate the mechanical behaviors of single-crystal magnesium (Mg) and graphene/magnesium (Gr/Mg) composites under compressive loading. Through the analysis of stress-strain curves, atomic structure diagrams, and dislocation distributions, the microscopic deformation mechanisms of single-crystal Mg and Gr/Mg composites under compressive loading were explored. Additionally, the influence of factors such as the number of Gr layers, loading strain rate, and temperature on the mechanical properties of the materials was studied. The results reveal that single-crystal Mg exhibits anisotropic characteristics under compressive loading. The addition of Gr enables the activation of difficult-to-initiate slip systems in the Mg matrix due to grain refinement. This leads to that stress is released, and the twinning deformation mechanism becomes difficult to initiate. Near the Gr interface, defects such as dislocations and twins nucleate and proliferate, effectively transferring the load to Gr, which elevates the average flow stress during the plastic deformation stage of the composites. Furthermore, the Mg matrix restricts the folding and bending of Gr, leading to an enhancement in material toughness. As a result, when the Gr/Mg composite is compressed along the [0 0 0 1] crystal direction to a strain of 0.35, the Gr remains intact without fracture. Dislocations in Gr/Mg composite materials cannot penetrate the Gr layer, which suppresses the damage of the Mg matrix. And the increase of dislocation lines can resist compressive plastic deformation. In composites with multiple layers of Gr, the yield stress, yield strain, and average flow stress during the plastic deformation stage increase with the increase in the number of Gr layers. Additionally, the yield strain is greater when the Gr layers are in a separated state compared to that in a stacked state. Within the temperature range of 10K-600K, the elastic modulus and yield stress of the Gr/Mg composite decrease with increasing temperature. However, the strain rate has an insignificant effect on the elastic modulus and average flow stress during the plastic deformation stage of the Gr/Mg composites. Nonetheless, increasing the strain rate can enhance the yield stress and yield strain of the composites.
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Received: 07 March 2024
Published: 27 December 2024
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2024, Vol. 45 
