The role of higher-symmetry phases in anisotropy of theoretical tensile strength of metals and intermetallics

Abstract

Fully self-consistent ab initio electronic structure calculation of the theoretical tensile strength of single-crystalline tungsten and NiAl loaded uniaxially along [001] and [111] directions is performed using the full-potential LAPW method. Although tungsten is elastically nearly isotropic (C ₄₄≈C'), theoretical tensile strength exhibits a marked anisotropy. Similarly, in NiAl, the ‘hard’ orientation [001] differs very significantly from the [111] orientation. This anisotropy is explained in terms of higher-symmetry structures present or absent along the deformation paths.