Scattering of Ultrasonic Radiation in Polycrystalline Metals

Abstract

A method for measuring absorption and velocity of ultrasonic radiation in the frequency range from 5 to 100 Mc by use of pulse techniques is described. Results of such measurements performed on polycrystalline magnesium and aluminum as a function of frequency and grain size show that the absorption coefficient varies linearly with frequency and inversely with grain size. The scattering power of a metal, and the fidelity with which an ultrasonic pulse is transmitted is shown to depend on the elastic constants of the single crystals. Criteria are established for evaluating the fidelity of pulse transmission in cubic and hexagonal metals, and figures of merit for many such polycrystalline metals are given.