Anisotropy in the elasticity of α-U from first-principles calculations and nanoindentation

ABSTRACT The anisotropic behavior of elastic properties of the low-temperature phase of uranium was studied by theoretical and experimental methods in this work. Firstly, based on the density functional theory, the elastic constants and compliance constants of α-U were obtained. Secondly, Young's modulus, bulk modulus, shear modulus, and Poisson's ratio of polycrystalline α-U were calculated using the Voigt-Reuss-Hill model. Then, according to the crystal symmetry of α-U, the spatial distribution characteristics of its Young's modulus were calculated and displayed. The Young's modulus of α-U in some specific crystal directions (including the typical deformation-induced twinning {1 3 0}, {1 7 2}) were also given. Nanoindentation method combined with electron backscatter diffraction (EBSD) technology were used to measure and characterize the grains with different crystal orientations, to obtain experimental values of Young's modulus of α-U in different crystal orientations. Also, the inverse pole figure of Young's modulus of α-U was given.