Characterization of Rolling Texture by Ultrasonic Dispersion Measurement

Ultrasonic scattering at grain boundaries in polycrystals causes attenuation of sound waves and dispersive sound velocities. Texture, that is a weighted orientation distribution of the grains, alters the ultrasonic propagation behavior directional dependent. An ultrasonic scattering theory presented in previous papers enables to calculate the complex propagation constants and hence the texture induced birefringence of sound waves in single-phase cubic polycrystals with rolling or fibre texture from single-crystal and texture properties. Inverted, the theory can be used for texture characterization from ultrasonic measurements. Based on the theoretical results, the influence of texture on the birefringence was calculated. For these calculations, the texture coefficients of rolled steel sheets and plates were evaluated from X-ray investigations, performed by other groups. A linear correlation was found between the frequence independent and the frequency dependent part of the ultrasonic birefringence. Ultrasonic investigations using rolled steel plates confirmed this linear interdependence. A first estimation of the analytical equations for the two parts indicate that the interdependence is governed by the single-crystal elastic moduli. The only supposition concerning texture is the orthorhombic symmetry. Based on these results, ultrasonic dispersion measurements enable the characterization of texture and hence the separation of texture and stress influences on the ultrasonic birefringence. This approach has the advantage that the actual degree of texture is taken into account.