Modern magnetostrictive materials Free

Two classes of magnetostrictive materials are emerging which can strongly impact magnetomechanical transduction and high‐stress antivibration systems. One class utilizes highly magnetostrictive rare earths with anisotropic 4f electron shells. The second class is based upon α−Fe, with substitutions of nonmagnetic Ga and Al for Fe. The first class contains three distinct types of materials: (a) hexagonal Tb_1−xDy_x alloys, (b) cubic CsCl type Tb_1−xDy_xZn alloys, and (c) cubic Laves phase Terfenol alloys. While the first two types produce extraordinarily high magnetostrictions only at cryogenic temperatures, Terfenol alloys exhibit large magnetostrictions (>1000 ppm) at 200<th>°C and above. This paper will focus on recent measurements on low‐hysteresis Terfenol‐DH alloys taken between −40<th>°C–+80<th>°C. The new class of promising high‐strength, low‐cost, Fe‐based alloys will also be introduced. Here the emphasis is on the development of a ductile, high tensile‐strength material with high strains (>300 ppm ), high relative permeabilities (>100), and low excitation fields (<300 Oe) under high loads. Magnetostriction, magnetization and elastic constant measurements as a function of stress and magnetic field will be presented. Values of piezomagnetic constants and coupling factors, calculated from these measurements, will be included. [Work supported by ONR.]