Propagation of Elastic Waves in Equiaxed Iron Polycrystals with Aligned  Axes
Thompson, R. Bruce
A polycrystalline material is composed of numerous discrete grains, each having a regular, crystalline atomic structure. The elastic properties of the grains are anisotropic and their crystallographic axes are differently oriented. Thus the anisotropic nature of elastic wave propagation in a number of structural materials, such as austenitic stainless steel welds and castings, used in nuclear power plants stems from the details of their grain structures. Columnar grain structure is seen in the austenitic stainless steel welds while the microstructure of cast stainless could vary from randomly oriented equiaxed grains to highly oriented columnar grains. An acoustic wave travelling through such a microscopically inhomogeneous medium suffers scattering and consequently has frequency dependent attenuation and phase velocity that depend on the grain structure. This paper is motivated by the desire to better understand these effects.