Construction And Application Of Multi-element EAM Potential In Ni-based Single Crystal Model Superalloys

Embedded-atom-method (EAM) potential includes important many-body effects based on the pair potential, which makes it widely used in the molecular dynamics (MD) simulations for pure metals and intermetallics. The reliability of the results from MD simulations is critically dependent on the reliability of the empirical potential. Ni-based superalloys are composed of nearly ten elements. Because the EAM potentials in the literature are mostly constructed for pure metals and binary alloys, the construction of multi-element EAM potentials is important for simulations about the movement of dislocations, crack propagation and alloying effects in the Ni-based single crystal superalloys. In the present work, the multi-element EAM potentials for Ni-based superalloys are constructed based on the Cai-Ye EAM potential and are applied to study the basic physical parameters of Ni-based superalloys.Cai-Ye EAM potential have been successfully used in the face-centered cubic (Fcc) metals and corresponding alloys. Cai-Ye EAM potential is parameterized as analytical functions with relatively fewer parameters. The metals with hexagonal-close packed (Hcp) structures have more constrains (two equilibrium conditions, five independent elastic constants and inner elastic constants) than Fcc metals (one equilibrium condition and three independent elastic constants). Thus, the application of Cai-Ye EAM potential in Hcp metals is relatively difficult. In the present study, the pair potential of Cai-Ye EAM is modified by adding an exponent function and a cut-off function to increase the flexibility in the fitting of the potential for Hcp metals. Moreover, the calculated stacking fault energy (SFE) of Fcc-Ni is also improved. The EAM potentials for Fcc-Ni, Al and Hcp-Re, Ru, Co are obtained by fitting the experimental values of their related physical parameters.γ’(Ni3Al) is an important strengthening phase in Ni-based single crystal superalloys. The Ni-Al potential is given by fitting the experimental physical parameters of γ’(Ni3Al). The planar faults in the γ’(Ni3Al) play an important role in strengthening alloys. The correlation between charge transfer, elastic constants and parameter s is found by considering the invariant transformation (f(r)â†'sf(r), F(p)â†'F(p/s)), the charge transfer and elastic constants constraint (C12-C44) in the present work. The planar fault energies calculated with EAM, such as SFE, are influenced by the consideration. These considerations make the embedding energy of the present potential has an important contribution to the planar fault energies. The mechanical properties of Ni-based single crystal superalloys are improved by the alloying elements, Re, Ru and Co. The Ni-Al-Re, Ni-Al-Ru, Ni-Al-Co and Ni-Al-Re-Ru EAM potentials are obtained by fitting the properties of virtual compounds calculated with first-principles method. The effects of alloying elements on the lattice misfit of γ(Ni)/γ’(Ni3Al) and the site preference of these elements in γ’(Ni3Al) are calculated with the present potentials. The results of the calculations from the present EAM potential are in agreement with those from first-principles. The SFE of Ni(Al,Co) random solid solution is calculated and the SFE decreases with increasing the concentrations of Al and Co. Thus, the cross-slip of screw dislocations can be inhibited and the alloy is strengthened. The interaction energy between Re atom and lattice misfit dislocation on the γ(Ni)/γ’(Ni3Al) is calculated, indicating a direct effect of Re atom on pinning effect of misfit dislocation.