Effect of defectiveness of carbon sublattice on elastic properties and microstrains of disordered cubic tantalum carbide TaCy

Abstract

Changes in the elastic constants cij of disordered cubic TaCy tantalum carbide with an increasing the defectiveness of the carbon sublattice are estimated for the first time. The deviation of tantalum carbide from the stoichiometric composition TaC1.0 leads to a decrease in the elastic stiffness constants cij of disordered TaCy carbide with a simultaneous increase in elastic anisotropy. The distributions of the Young's modulus E and the Poisson's ratio μ in the (100) plane and the distributions of the shear modulus G in the (100), (110), and (111) planes have been calculated as functions on the crystallographic direction [hkl] and on the relative carbon content y in TaCy carbide. The Vickers hardness HV of disordered tantalum carbide was calculated using the inverse Pugh's ratio G/B and the experimental data on the dependences of the bulk modulus B and the shear modulus G on the composition of disordered TaCy. Influence of nonstoichiometry of nanocrystalline powders of cubic tantalum carbide TaCy on anisotropy of strain distortions is established. The value of microstrains εhkl is estimated with allowance for their anisotropy.