The scattering of ultrasonic waves by multiphase polycrystals.

The theory of ultrasonic propagation in single-phase polycrystals presented in previous articles (J.Acoust.Soc.Am 72,1021-1031 (1982); 73, 1160-1163 (1983)) is generalized to calculate the scattering coefficients and phase and group velocities of plane compressional and shear waves in multiphase polycrystals. The analytical calculation was done for macroscopically isotropic materials with phases of cubic, hexagonal, or orthorhomic single-crystal symmetry in second-order perturbation theory using the assumption that the relative mean quadratic deviation of the wavenumbers in the polycrystal considered from its homogeneous isotropic approximation is small. Numerical evaluation is carried out for a two-phase material of alpha- und gamma-Fe. (IZFP)