Molecular dynamics study of mosaic structure in the Ni-based single-crystal superalloy

The mosaic structure in a Ni-based single-crystal superalloy is simulated by molecular dynamics using a potential employed in a modified analytic embedded atom method. From the calculated results we find that a closed three-dimensional misfit dislocation network, with index of \langle 011\rangle100 and the side length of the mesh 89.6?, is formed around a cuboidal \gamma ' precipitate. Comparing the simulation results of the different mosaic models, we find that the side length of the mesh only depends on the lattice parameters of the \gamma and \gamma ' phases as well as the \gamma /\gamma ' interface direction, but is independent of the size and number of the cuboidal \gamma ' precipitate. The density of dislocations is inversely proportional to the size of the cuboidal \gamma ' precipitate, i.e.~the amount of the dislocation is proportional to the total area of the \gamma /\gamma ' interface, which may be used to explain the relation between the amount of the fine \gamma ' particles and the creep rupture life of the superalloy. In addition, the closed three-dimensional networks assembled with the misfit dislocations can play a significant role in improving the mechanical properties of superalloys.