Influence of Preferred Orientation on Ultrasonic Grain Scattering

The known formulas for ultrasonic attenuation caused by scattering in metals are inapplicable when the metal exhibits preferred orientation. It is shown through the analysis of a two-dimensional mathematical model of the elastic anisotropy of a grain that preferred orientation tends to reduce the anisotropy factor in the grain scattering formulas. It is inferred that the scattering will be nil in heavily rolled hcp metals (where the c axes of the grains are aligned) and in heavily rolled and recrystallized fcc metals (where a ``cube texture'' develops with alignment of all the axes). Experiments on these and other plastically deformed metals will prove valuable. One experiment on zinc bar stock is described to demonstrate the reduction of scattering by preferred orientation. Scattering of longitudinal waves was lower along the bar axis than perpendicular to it since the preferred orientation yielded only a axes of grains along the bar axis but both a and c axes pointing radially.