石墨烯/铝基复合材料在纳米压痕过程中位错与石墨烯相互作用机制的模拟研究

Simulation of interaction behavior between dislocation and graphene during nanoindentation of graphene/aluminum matrix nanocomposites

石墨烯因其优异的力学性能已成为增强金属基复合材料的理想增强体.然而,目前对石墨烯/金属基复合材料在纳米压痕过程中嵌入石墨烯与位错之间的相互作用仍不清晰.本文采用分子动力学模拟方法,对90°,45°和0°位向的石墨烯/铝基复合材料进行了纳米压痕模拟,研究了压痕加载和卸载过程中石墨烯/铝基复合材料的位错形核及演化,以获取不同位向的石墨烯与位错的相互作用机制,并分析其对塑性区的影响.研究发现,石墨烯可以有效阻碍位错运动,并且石墨烯会沿着位错滑移方向发生弹性变形.在纳米压痕过程中,位错与不同位向石墨烯之间的相互作用差异导致塑性区的变化趋势不同.研究结果表明,在石墨烯/铝基复合材料中,位向不同的石墨烯对位错阻碍强度和方式不同,且石墨烯位向为45°的复合材料的硬度高于其他模型.此外,石墨烯/铝基复合材料的位错线总长度的演化规律与石墨烯位向紧密相关.本文研究可为设计和制备高性能石墨烯/金属基复合材料提供一定的理论指导.

Graphene has been thought to be an ideal reinforcement material for metal matrix composite due to its superior mechanical properties and unique two-dimensional geometry.However,the deformation mechanism of graphene/aluminum matrix composite is still unclear.In this paper,molecular dynamics simulation is used to elucidate the evolution details of the dislocation microstructure and the underlying interaction behavior between dislocation and graphene during nanoindentation of the graphene/aluminum matrix composite with various graphene orientations.To this end,four different cases,i.e.the pure aluminum and the graphene/aluminum matrix composite with the graphene orientation of 90°,45°and 0°are examined,respectively.Based on the force-indentation depth curve,the interaction behavior between dislocation and graphene and its effect on the plastic zone are analyzed.The results indicate that the graphene can act as an effective dislocation motion barrier,and the elastic deformation of graphene can occur locally along the direction of dislocation slip.Using the visualization technique of dislocation extraction algorithm,the nucleation and propagation of dislocation are investigated.The results show that the differences in interaction behavior between dislocation and graphene with various orientations affect the spreading trend of the plastic zone and the blocking strength of graphene to dislocation.For the composite with the graphene orientations of 45°and 0°,the interaction between graphene and dislocation causes the number of dislocations to increase.Additionally,the plastic zone of the composite with the graphene orientation of 45°is tangent to two symmetrical graphene sheets.For the composite with the graphene orientation of 90°,the interaction between graphene and dislocation shortens the total length of the dislocation line,and the volume shrinkage of plastic zone is most significant after indenter retraction.Here,the hardness is also calculated to quantitatively evaluate the influence of graphene orientation on the mechanical properties of graphene/aluminum matrix composite.The hardness of the composite with the graphene orientation of 45°is highest,which is due to the decrease of the volume of the plastic zone and the increase of dislocation number.The decrease of the hardness of the composite with the graphene orientation of 90°is attributed to the reduction of dislocation number in the plastic zone.However,for the composite with the graphene orientation of 0°,the interaction between graphene and dislocation results in the softening effect,because of a wide range of elastic deformation in the graphene plane.The study can provide a certain theoretical guidance for designing and preparing the high-performance graphene/metal matrix composites.