MD simulations of strengthening by graphene in iron crystals

在铁合金中，固溶强化、析出强化和晶界强化所引起的强度提高在材料的技术应用中起着突出的作用。在这个项目中，纳米级石墨烯盘嵌入到铁基体和碳固溶体的机械性能的影响，分别通过从头算和分子动力学（MD）模拟研究。石墨烯盘的添加预期改善若干机械性质。特别地，石墨烯盘的热稳定性和铁/石墨烯复合材料的弹性、强度和塑性的性质是重要的。为了估计石墨烯盘的热稳定性，进行从头计算模拟，其也用于改进MD模拟的原子间势。使用单晶和多晶的分子动力学模拟将针对不同的温度、碳和石墨烯浓度，以及不同尺寸、距离和石墨烯盘的取向进行。模拟的目标是关于位错/沉淀相互作用、应力场和由石墨烯盘或合金碳原子引起的晶格中的残余应力的基本发现，以及这些材料的机械性能的相关变化。第一次，MD模拟用于研究是否以及在何种程度上可以通过在最大强度的期望方向上添加石墨烯盘来分别改善铁的性能，同时具有最大弹性和最佳可能的塑性变形能力（延展性和断裂应变）。

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.