ACOUSTIC CHARACTERIZATION OF METALS WITH COLUMNAR GRAINS

Acoustic characterization measurements of Sn, Pb, Al and Cu metallic a lloys with highly oriented columnar grains are presented. Using a 225 MHz line-focus-beam scanning acoustic microscope we have observed the ultrasonic anisotropy of a transversely isotropic symmetry for small g rain width (similar to acoustic wavelength) samples. The long needle g rain structures induce unique acoustic anisotropic characteristics, su ch as focussing and diverging, which have been illustrated in the guid ed longitudinal and shear acoustic wave pulse-echo measurements perfor med for rod geometry. The understanding of elastic anisotropy is of im portance for non-destructive testing of such materials.