Nanocrystalline materials are polycrystalline by less than 100 nanometer grain size that in comparison between nanocrystalline and polycrystalline materials, nanocrystalline have high atomic fraction in grain boundaries that these area cause to grain growth. So due to maintenance the nanocrystalline's special properties, should avoid of grain growth. In this research, the aim was study about grain growth of pure Aluminiom and Aluminiom-1% at Magnesium nanocrystalline, that is studied on bicrystalline and triple junction and quad nods by using Molecular Dynamics simulation, utilization Lammps cod. These structure were made by Python and the structure by 1% at Mg, Mg was substituded by Al elements that were place in high energy area. In bicrystalline was searched about the influence of grain boundary curvature, temperature and grain boundary's angle on the Al bicrystal's grain growth. In order to potential energy diagrams and graphical picture of grain growth and the diagram of mean squared displacement versus time, it was shown that the necessary condition for grain growth is the grain boundary's curvature and the grain growth continue until this curvature existence. This curvature was made tension and compression areas that were caused gradiant in potential energy and also was proofed by Gibs-Thamson equation. This gradiant are the driving force for short range diffusion. Also for the influence of temperature on grain growth, was studied on 500, 650 and 750 K, it is shown that the rate of grain growth, that is diffusin coefficient, increase by increasing the temperature. About the influence of grain boundary's angle by increasing the angle from 18.8° to 28.3° the potential energy increased. Due to avoid the grain growth, 1% atomic Mg were entered to grain boundary accidently. The result were shown that Mg move to compression area of grain boundary and causes the potential energy's gradient, (i.e. diffusion's driving force), tend to zero and stop the grain growth. In triple and quad junction, the grain growth continue until the curvature of grain boundaries existence. Also, by entering the 1% atomic Mg in Tj and Qn's area the grain growth stop. Finally, in this study was shown that the Gibs-Thamson equation is approved in atomic scale and we can use the Molecular Dynamics simulastion for recognizing the grain growth in atomic scale. Keywords: Nanocrystalline, Grain Growth Mechanisms, Molecular Dynamics Simulation, Entering the Solution Element, Triple junction, Quad nods.
