Acoustic characterization of metals with long needle grains

Acoustic characterization measurements of Sn, Pb, Al, and Cu metallic alloys with highly oriented long needle grains are presented. Using a 225-MHz line-focus-beam scanning acoustic microscope, the ultrasonic anisotropy of a transversely isotropic symmetry for samples having small primary dendrite spacings ( approximately acoustic wavelength) samples is observed. The column grain structures induce unique acoustic propagation characteristics, such as focusing and diverging, which are illustrated in the guided longitudinal and shear acoustic wave pulse-echo measurements performed for rod geometries.<>