MD simulations of strengthening by graphene in iron crystals

在铁合金中，固溶、析出和晶界强化引起的强度提高在材料的技术应用中起着突出的作用。本项目采用从头计算和分子动力学(MD)模拟的方法，分别研究了纳米石墨烯镶嵌在铁基中和碳在固溶体中对其力学性能的影响。石墨烯圆盘的加入有望改善几种机械性能。特别是，石墨烯圆盘的热稳定性以及铁/石墨烯复合材料的弹性、强度和塑性性能是非常重要的。为了估计石墨烯圆盘的热稳定性，我们进行了从头算模拟，这也被用来改进分子动力学模拟的原子间作用势。分子动力学模拟将在不同温度、碳和石墨烯浓度以及不同尺寸、距离和取向的石墨烯圆盘上进行。模拟的目标是关于石墨烯圆盘或合金化碳原子在晶格中引起的位错/沉淀物相互作用、应力场和残余应力的基本结果，以及这些材料力学性能的相关变化。首次使用分子动力学模拟来研究在具有最大弹性和最佳塑性变形能力(延性和断裂应变)的期望方向上添加石墨烯圆盘是否可以改善铁的性能以及在多大程度上改善铁的性能。

In iron alloys, the increase in strength caused by solid solution, precipitate and grainboundary strengthening, plays an outstanding role in the technical application of the materials. In this project, the influence of nanoscale graphene discs embedded into the iron matrix and of carbon in solid solution on the mechanical properties, respectively, is investigated by means of ab initio and molecular dynamics (MD) simulations. The addition of graphene disks is expected to improve several mechanical properties. In particular, the thermal stability of the graphene discs and the properties of elasticity, strength and plasticity of the iron/graphene composite material are of importance. To estimate the thermal stability of the graphene discs, ab initio simulations are performed, which are also used to improve the interatomic potentials for the MD simulations. Molecular dynamics simulations using single- and polycrystals will be performed for different temperatures, carbon and graphene concentrations, as well as for different sizes, distances and orientations of the graphene discs.The objectives of the simulations are fundamental findings concerning dislocation/precipitate interactions, stress fields and residual stresses in the crystal lattice caused by the graphene discs or alloyed carbon atoms, and the associated changes in the mechanical properties of these materials.For the first time, MD simulations are used to investigate whether and to which extent the properties of iron can be improved by the addition of graphene discs in the desired direction of maximum strength with maximum elasticity and best possible plastic deformability (ductility and fracture strain) respectively.