Lattice distortion effect on elastic anisotropy of high entropy alloys

Abstract

The superior mechanical properties of high-entropy alloys (HEAs) have made an outstanding success in materials science and engineering. Studies to date have been devoted to what the severe lattice distortion induces. However, most researchers focus on its stimulation to plastic deformation instead of scrutinizing the variations on elasticity. Compared with conventional alloys, HEAs may perform disproportionate elasticity with uneven local lattice strain resulting from the severe lattice distortion. Therefore, it is necessary to survey its influence on the mechanical properties of HEAs systematically. In this study, the Lennard-Jones (LJ) potential, the embedded atom method (EAM) potential, and the modified embedded atom method (MEAM), are respectively conducted to investigate the lattice distortion effect on Young’s modulus E (hkl) and Poisson’s ratio ν (hkl, θ) along [100], [110], and [111] loading directions for several fcc metals composed of 1 ∼ 5 atomic types, including Ni, Ni98W2, Ni96W4, FeCrNi, and CoNiCrFeMn HEAs. Also, a method is used to analyze the performance of the individual element on the elastic properties in the HEA environment. As a result, it can be unveiled that the effect of electron density inconsistency is more dominant than the effect of lattice distortion associated with the atomic size difference. The electronic configuration in the HEA environment plays a major role in elastic anisotropy while the difference of the atomic radii does the minor one. The anisotropy of CoNiCrFeMn HEA analyzed by this work is also consistent with in-situ neutron diffraction measurements.