EFFECT OF HEAT-TREATMENT ON THE MAGNETOSTRICTION AND MICROSTRUCTURE OF TERFENOL-D

Grain aligned rods of the highly magnetostrictive Terfenol compound (D y0.73Tb0.27Fe1.9) prepared by vertical float zoning have been heat tre ated in order to study the influence on the magnetostriction and micro structure. A significant improvement (10-20%) in the magnetomechanical coupling coefficient was observed on samples treated at 1000-degrees- C for 24 h; further enhancement could be obtained by increasing the tr eatment time to 7-10 days. A k33 value of 0.82 has been recorded on a rod treated in this way. The associated microstructural changes involv e a re-distribution of the RE-rich phase, in particular a re-absorptio n of the intra-grain species into the matrix, thus removing obstacles to domain wall motion.