The alloy $Tb_xDy_{1-x}Fe_y$ (0.27≤x≤0.30, y≤2), which is called Terfenol-D, is known to have gaint magnetostriction and comparatively low magnetocrystalline anisotropy energy. Therefore high strain amplitudes, approaching 1000 ppm, can be obtained at low field (<100 kA/m). This thesis is composed of seven sections related with manufacturing of terfenol-D, which are calculation of the ternary phase diagram, manufacturing of feeder rods, Bridgman crystal growth, zone melting method, magnetization modeling of terfenol-D, polymer infiltrated grain aligned composite terfenol-D and measurement of magnetic properties.
The Tb-Dy-Fe ternary phase digram was calculated with ThermoCalc software. Tb-Fe and Dy-Fe systems were assumed to form regular solution and Tb-Dy assumed to be ideal solution. Any ternary interactions were ignored. Formation free energies of 8 kinds of intermetallic compounds were quoted from the literature.
Feeder rods were cast by vacuum suction method. The apparatus was developed in this work to make feeder rods of uniform composition and shape with higher productivity in a shorter time. The cast rods were analyzed to be very uniform in composition and have a strong directionality. Moreover, elemental loss in this process was negligible compared with an arc melting method.
There was severe macrosegregation in Bridgman grown crystals, which caused high fluctuation in saturation magnetostrictions of each part of the crystal. It was due to the solute gradient in the initial melt, which could be eliminated by stirring the melt by force.
Preferred orientation of $RFe_2$ dendrites was 110 at low velocity regime, on the contrary it was 112 at high velocity regime. The change of texture was analyzed with the help of pole figures and orientation distribution functions.
Magnetization of terfenol-D was modeled with ADR(Anistropic Domain Rotation) model which was originally attempted by Jiles. Magnetization of poly crystal terfenol-D which have several textures was calculated by superposing the magnetostriction of each constituent single crystal. Magnetostrictive coefficient as well as differential permeability were compared with experimental results, too.
New polymer composite was developed to enhance the electric resistivity, while maintaining its gaint magnetostriction. RE phase was removed from terfenol-D by high temperature heat treatment, thereafter polymer resin was infiltrated into the void space where RE phase had existed. Magnetostriction, $d_33$, $k_33$ and electric resistivity were higher than those of as-grown crystals. Therefore it was successful to make a polymer composite which could solve inherent problems of previous composite materials.
