A coarse-grained-Atomistic multi-scale method to study the mechanical behavior of heterogeneous FCC nano-materials

AA Madadi and AR Khoei, COMPUTATIONAL MATERIALS SCIENCE, 199, 110725 (2021).

DOI: 10.1016/j.commatsci.2021.110725

In this paper, a multi-scale method is developed to couple the atomistic domain with the coarse-grained system to model the mechanical properties of materials with defects and heterogeneity. The material properties are determined in the nano-scale level by Molecular Dynamics analysis, in which the interatomic potential is used to determine the interaction between the particles. The main issue with the Molecular Dynamics method is its high computational cost. Hence, the coarse-grained method is employed, where a number of atoms are assumed as a bigger bid, and the interatomic potential is modified in terms of the position of the grains. This method reduces the computational cost as the degrees of freedom decreases. Moreover, it has the advantage of using the same interatomic potential as molecular dynamics method comparing to the continuum-based approaches. One issue with the coarse-grained method is that phenomena with small wavelengths cannot be captured comparing to the all-atoms system. To this end, a multi-scale method is presented to couple the atomistic domain with the coarsegrained system. In this method, the regions near to the cracks, defects, or heterogeneity are modeled by the conventional MD scheme and farther regions by the coarse- grained method. In order to illustrate the capability of the proposed computational model, the evolution of misfit dislocation is investigated at the interface of Ni3Aland Ni, which is formed by their subtle difference in lattice parameter. Obviously, dislocations play a crucial role in determining the mechanical behavior of superalloys even though a considerable number of atoms are located in perfect lattice-structures, and dislocations comprise a small region of the domain. Thus, it is rational to apply the proposed CG-MD multi-scale method to study the mechanical behavior of such materials. Finally, the effect of loading and temperature is investigated on dislocation density of the Ni-based superalloys using the CG-MD multi-scale method; it is shown that dislocation density increases as the temperature or strain increases.

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