石墨烯对镁基复合材料抗压性能影响的分子动力学研究  

Molecular Dynamics Study of the Effect of Graphene on the Compressive Properties of Magnesium Matrix Composites

作　　者：华军 邢小茹 谢云龙 赵冬 Jun Hua;Xiaoru Xing;Yunlong Xie;Dong Zhao(School of Science,Xi'an University of Architecture and Technology,Xi'an,710055)

机构地区：[1]西安建筑科技大学理学院力学系,西安710055

出　　处：《固体力学学报》2024年第6期776-794,共19页Chinese Journal of Solid Mechanics

摘　　要：镁(Mg)作为轻质金属材料,因其塑性不足及高温下力学性能下降等缺点限制了其应用.石墨烯(Gr)因其比表面积大、强度高等优点可以作为一种理想增强材料与金属镁复合,从而提升材料的力学性能.本文采用分子动力学(MD)方法对石墨烯/镁(Gr/Mg)复合材料在不同压缩条件下的力学性能进行研究.结果表明,单晶Mg在不同晶向下压缩表现出强烈的各向异性特征.引入Gr使得Mg基体中难以启动的滑移系因晶粒细化作用而被激活,应力得到释放,孪生变形机制难以开启.位错和孪生等缺陷在Gr界面附近形核增殖,载荷有效传递至Gr,提升了复合材料塑性阶段的平均流动应力.此外,Mg基体对Gr的约束限制了Gr的褶皱和弯曲,使材料韧性增强,Gr/Mg复合材料沿Z轴[0 0 0 1]晶向压缩的应变达0.35时,Gr仍未断裂.Gr/Mg复合材料中位错运动到Gr表面无法继续贯穿,抑制了Mg基体的破坏.压缩荷载作用下,Gr/Mg复合材料中位错线的增加有助于抵抗压缩塑性变形.Gr/Mg复合材料的屈服应力、屈服应变及塑性变形阶段的平均流动应力随着Gr层数增加而增大,且Gr处于分离状态时,Gr/Mg复合材料的屈服应变更大.在10K~600K温度范围内,Gr/Mg复合材料的弹性模量和屈服应力随着温度升高而降低.而应变率对Gr/Mg复合材料的弹性模量和塑性变形阶段的平均流动应力影响不明显,但增大应变率可以提高复合材料的屈服应力和屈服应变.Magnesium(Mg),a lightweight metal material,is constrained in its applications due to poor plasticity and low strength at high temperatures.Graphene(Gr) possesses a large specific surface area and high strength,making it an ideal reinforcement for improving the mechanical properties of materials.A molecular dynamics(MD) simulation was employed to investigate the mechanical behaviors of single-crystal Mg and 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 materials was studied.Results reveal that single-crystal Mg exhibits anisotropic characteristics under compressive loading.Addition of Gr enables the activation of difficult-to-initiate slip systems in the Mg matrix due to grain refinement.This leads to stress release and difficulty in initiating twinning deformation.Near the Gr interface,defects such as dislocations and twins nucleate and proliferate,effectively transferring the load to Gr,thereby elevating 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,thus suppressing Mg matrix damage.Increased dislocation lines can resist compressive plastic deformation.In composites featuring multiple layers of Gr,the yield stress,yield strain,and average flow stress during the plastic deformation stage increase with the number of Gr layers.Additionally,the yield strain is higher when Gr layers are separated compared to

关 键 词：石墨烯 镁基复合材料 压缩力学性能 分子动力学 位错 

分 类 号：TB333[一般工业技术—材料科学与工程]