The Fe/Ni Multilayers Mechanical Property Size Effects By Molecular Dynamics Simulation

The micro performance study has important guiding significance for the wide application of thin film material. How to correct characterization of the micro performance has become one of the highlights research in the thin film materials currently. In this article, molecular dynamics simulation methods is used to simulate the Fe/Ni multilayer film with uniaxial tensile. To explore the same modulation ratio and different modulation ratio of Fe/Ni multilayer film yield stress relationship with the thickness of single layer. Analyzed the microstructure revolution of Fe/Ni multilayer film and the strengthening mechanism in the process of tension. The main conclusions as follows:1. The same modulation ratio of Fe/Ni multilayer film tensile simulation results show that the yield stress of Fe/Ni multilayer film has deeply dependence on the thickness of single layer, the main reason is because of its deformation mechanism has changed. The variation trend of yield stress of Fe/Ni multilayer film can be roughly divided into three stages. When the thickness of single layer greater than15.18 nm, the yield stress of thin film increase with the decrease of the thickness of single layer, follow the classic Hall-Petch relationship, the deformation mechanisms is dislocation pile-up; When the thickness of single layer at the middle of 10.6 nm to15.18 nm. the yield stress do not increase again and show a certain range of fluctuation, at this time, the deformation mechanism is dislocation bow out of the mechanism; When the thickness of single layer further reduced, the yield stress decreases with the decrease of the thickness of single layer, which accord with the reverse Hall-Petch relation, the deformation mechanisms of thin film is the dislocation across the interface.2. The different modulation ratio of Fe/Ni multilayer film tensile simulation results shows that when the layer thickness of Ni unchanged and the layer thickness of Fe changed, the layer of Fe structure will disorder with the decrease of the Fe layer thickness, the smaller the size, the deeper degree of disorder. This phenomenon shows that in the structure of Fe/Ni multilayer thin film, the layer of Fe is the first to yield, it is the “soft” organization in the Fe/Ni multilayer film. When the layer thickness of Fe unchanged and the layer thickness of Ni changed, the yield stress of Fe/Ni multilayer film will decreased with the increase of the layer thickness of Ni, When reduced to acertain value began to increase, and then the yield stress within a certain range of fluctuation. At the same time, Young’s modulus increased with the increase of the layer thickness of Ni.