Modeling of magnetostriction in grain aligned terfenol-D and preferred orientation change of terfenol-D dendrites

Abstract

The alloy Tb 0.3Dy 0.7Fe 2 (terfenol-D) is known to have high magnetostriction and low anisotropy energy. Therefore, comparatively high strain amplitudes, approaching 1000 ppm, can be obtained at low field (<100 kA/m). It was found that terfenol-D zone melted without seed was a polycrystal with preferred orientations. For a polycrystal, where several different fiber textures are mixed, we used an anisotropic domain rotation model to predict its magnetostriction and magnetization. This model, originally proposed by Jiles, assumed that the magnetic moments of domains are constrained by the anisotropy to lie along the 〈1 1 1〉 easy magnetization directions. The magnetostrictive properties of such a polycrystal were estimated by superposing the individual properties of all constituent grains relative to their volume fractions. The volume fractions of the constituent textures were calculated using orientation distribution functions. The results showed that the preferred orientation of terfenol-D dendrites changed from 110 to 112 with the increase of growth velocity. The model showed good qualitative agreement with experimental results, for magnetostriction of grain aligned polycrystalline Tb 0.31Dy 0.69Fe 1.80 with applied magnetic field under a range of constant uniaxial compressive stresses.