Characterization of rolling texture by ultrasonic dispersion measurement
In polycrystals ultrasonic waves are scattered at grain boundaries. This causes attenuation of the waves and dispersive sound velocities. In textured polycrystals the velocities and scattering coefficients are not only dependent on frequency but also on direction. A theory on ultrasonic propagation in polycrystals presented in previous papers (1,2) allows to calculate the complex propagation constants of plane ultrasonic waves in single-phase polycrystals with texture of orthorhombic symmetry. The yielded results can be used to determine texture coefficients from the directional dependence of measured sound velocities. Mechanical stress, too, alters the velocities of ultrasonic waves directional dependent, and the effects of stress and texture are superposed. In this case, the fact that contrary to stress texture causes frequency dependent velocity alterations with direction can be exploited. That is, a method is required to determine texture coefficients only from the frequency depend ent part of the sound velocities. Previous calculations (3) with data taken from the literature suggest the assumption that there is a connection between the frequency dependent and the constant part of ultrasonic birefringence if the consideration is restricted to a fixed material with a fixed type of texture. This paper presents calculations and experiments to confirm this assumption for rolled plates.