Ultrasonic Backscattering in Cubic Polycrystals with Ellipsoidal Grains and Texture

An ultrasonic model for backscattering from polycrystalline microstructure is developed for polycrystals with uniaxial texture and elongated cubic crystallites. The uniaxial texture or crystallographic orientation of the grains is described by a modified Gaussian orientation distribution function (ODF) with a texture parameter. Macroscopically such a textured polycrystalline medium exhibits hexagonal symmetry. The preferred texture direction and elongation are independently defined in a global system. The dependence of backscattering coefficients and their directional ratios on both texture and grain anisotropy are discussed. Attenuation coefficients in the high frequency range for arbitrary wave propagation direction are obtained and then the ratios in the three axis directions are studied. The model is compared with experimental data available in the literature for Al rolled alloys and shows good agreement when accounting for both texture and grain anisotropy effects.