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 < 011 >{100} and the side length of the mesh 89.6 angstrom, 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.