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

Ni-based single crystal(SC)superalloys have been widely used in turbine blades of aero engines due to their superior high-temperature strength and creep resistance.In order to improve the mechanical and chemical properties,more than ten alloying elements are added into superalloys.Experiments and exploratory researches have been widely carried out to study the role of these alloying elements.Molecular dynamics(MD)simulation is an efficient method to study the atomic mechanism of solute elements on the mechanical properties of superalloys.An appropriate interatomic potential is crucial for MD simulations and affect the reliability of the simulation result.Based on experiments and first-principles calculations,ternary Ni-Al-X(X=W,Ta)and quaternary Ni-Al-Re-W embedded-atom-method(EAM)potentials are constructed by considering the invariant transformation of the potential parameters,elastic constants constraint and the charge transfer between the atoms.These potentials are applied in the physical properties and the dislocation movement in superalloys.The EAM potential for BCC-W and BCC-Ta are constructed by fitting the basic physical properties.The energy of structure stability,the surface energies and the generalized stacking fault energy profile(y-surface)are also calculated with the present potential.The simulation results are basically consistent with the experimental data or the first-principles calculations.The potential predicts that W atoms do not tend to form clusters in y(Ni),which is consistent with experiments.The impurity diffusion of W in y(Ni)is investigated using the five-frequency model.The effective diffusion activation energy Qe and the pre-exponential factor D0 are in reasonable agreement with the data in literatures.By W doping,the lattice misfit between the two phases decreases and the elastic constants of ?'(Ni3Al)increase.Due to the:more negative binding energy of Ni-W,the pinning effect of W on the ?(Ni)/?'(Ni3Al)interface misfit dislocation is stronger than that of Re.As for alloyed elements Co.Re and W,the pinning effect of solute atom on the ?(Ni)/?'(Ni3Al)misfit dislocation increases with the increasing of the atomic radius.Ta is an effective element for solid-solution hardening and mostly in participated in ?' phase.The planar fault energies of Ni3Al calculated with the potential increase with the addition of Ta.The motion of a[110]edge superdislocation in the(001)cubic plane of y'(Ni3Al,Ta)is investigated using MD method.The motion mechanism of the dislocation under different shear strains is proposed.The simulation results reveal that the edge dislocation has a very jerky movement,and both complex Lomer-Cottrell locks and dislocation dipoles are formed in the slipping process.The addition of Ta can decelerate the motion of edge dislocations and inhibit the production of dislocation dipoles.The present study provides valuable insight into the effect of Ta on the superdislocation mobility of ?'(Ni3Al).