First-principles calculations for the elastic properties of Ni-base model superalloys: Ni/Ni₃Al multilayers

A model system consisting of Ni001(100)/Ni₃Al001(100) multi-layers are studied using the density functional theory in order to explore the elastic properties of single crystal Ni-based superalloys. Simulation results are consistent with the experimental observation that rafted Ni-base superalloys virtually possess a cubic symmetry. The convergence of the elastic properties with respect to the thickness of the multilayers are tested by a series of multilayers from 2\gamma'+2\gamma to 10\gamma'+10\gamma atomic layers. The elastic properties are found to vary little with the increase of the multilayer's thickness. A Ni/Ni₃Al multilayer with 10\gamma'+10\gamma atomic layers (3.54 nm) can be used to simulate the mechanical properties of Ni-base model superalloys. Our calculated elastic constants, bulk modulus, orientation-dependent shear modulus and Young's modulus, as well as the Zener anisotropy factor are all compatible with the measured results of Ni-base model superalloys R1 and the advanced commercial superalloys TMS-26, CMSX-4 at a low temperature. The mechanical properties as a function of the \gamma' phase volume fraction are calculated by varying the proportion of the \gamma and \gamma' phase in the multilayers. Besides, the mechanical properties of two-phase Ni/Ni₃Al multilayer can be well predicted by the Voigt-Reuss-Hill rule of mixtures.