Multiscale evaluation of the elastic response of polycrystalline NiAl using molecular statics, EBSD-based finite element and analytical homogenization methods

Abstract

The presented work proposes a multiscale framework for the numerical and analytical determination of the elastic constants of the intermetallic nickel aluminide (NiAl) at the microscopic scale. Molecular dynamics (MD) calculations have been employed to evaluate the stiffness tensors of a single NiAl monocrystalline body with cubic Pm$\bar{3}$m symmetry. The atomistic results were transferred to the upper scale as an input to micromechanical models. Here, finite element modeling (FEM) and analytical homogenization methods were used to simulate the elastic behavior of polycrystalline NiAl, with special attention to grain anisotropy and its morphology. The microstructural features of the heterogeneous body were evaluated experimentally using electron backscatter diffraction (EBSD) and subsequently used to generate a 3D polycrystalline geometric model that preserves realistic distributions of grain orientations and grain sizes. The reconstructed NiAl polycrystal was subjected to uniaxial tensile test simulations using FEM to evaluate the effective Young's modulus ($E$) and Poisson's ratio ($ν$). The numerical results were confronted with the experimental values of $E$ and~$ν$. With these model assumptions, a very good agreement between numerical and experimental results was achieved. Finally, the experimental results were compared with classical analytical estimates. Among the analytical approaches, the Hashin-Shtrikman upper bound and self-consistent approximation reproduced the experimental Young's modulus with minor deviations.