Influence of microstructural features on the effective magnetostriction of composite materials

Recently developed magnetostrictive composites of a giant magnetostrictive alloy and an inactive matrix have opened up a promising territory for the application of materials with magnetic-mechanical coupling interactions. In this article an effective-medium method is developed for the effective magnetostrictive behavior of such composite materials based on a Green’s-function technique. Explicit relations for determining the effective magnetostriction of the spherical particulate and fibrous composites with elastically isotropic magnetostrictive crystallites are derived. Two extreme bounds—the Reuss and Voigt-type bounds—are also given. To illustrate the technique, numerical calculations for the effective saturation magnetostriction of SmFe₂/epoxy or aluminum and Terfenol-D/epoxy or aluminum composites with various phase compositions, particle shapes and orientation, and crystallite growth directions, are performed. The theoretical estimates are found to be in agreement with available experimental results, and they also show the interesting magnetostrictive behavior of the composites.