Papers by Author: Chihiro Saito

Abstract: Polycrystalline Galfenol (Fe-Ga-X, X=Al, C, Zr etc.) alloys were fabricated as a bulk sample from rapid-solidified powders or ark-melted and annealing process method for enhancing various engineering applicabilities of this magnetostrictive alloy. Especially, (Fe-Ga0.15-Al0.05)99.0-Zr0.5-C0.5 [at.%] sample showed a maximum magnetostriction of λmax=90ppm to 150ppm as well as a tensile stress over σ=800MPa. This large magnetostriction is mainly caused by non-precipitating of the ordered A2 phases without the excessive precipitation of ordered phases such as fcc ordered L12, bcc ordered D03 phases and the remained [100] oriented strong textures by a heat treatment. Based on the improvements of these properties in the developed bulk Galfenol alloys, secondarily, we will introduce an application as a smart torque sensor by utilizing Galfenol-ring around the shaft for steering-by-wire system of automobile. A torque sensing system by using the magnetostrictive ring of Galfenol alloy was developed and magnetic flux leakage from the ring attached on the rotating shaft was experimentally measured by using differential Hall probe sensor. The sensitivity of this type of torque-sensor shows a strong dependency of metallurgical microstructure and the residual stress (i.e.hoop-stress) in the ring due to sensor shows a strong dependency of the residual stress (i.e.hoop-stress) in the ring due to the fitting level. A promising result on ring-type and single-structured inverse magnetostrictive torque sensor will be presented.

Abstract: Magnetoelectric(ME) coupling in multi-ferroic composite designed by using two material elements of Pb(Zr, Ti)O3 (PZT: 260μm) and magnetostrictive alloys(Galfenol based Fe-Ga-X(X=Al, Co), ferromagnetic shape memory Fe-Pd) was investigated. Output ME Voltage under the driving a.c.magnetic field Hac at f = 1 Hz in Fe81Ga19/PZT/ Fe81Ga19, Fe80Ga15Al5 /PZT/ Fe80Ga15Al5, Fe76Ga17Co7/PZT/ Fe76Ga17Co7 composites, in which the magnetostrictive foils(50μm thickness) were prepared by rapid solidification, increased in proportion to the actuated force than the magnetostriction.Moreover，output ME Voltage in Fe70Pd30 / PZT/ Fe70Pd30 laminates, in which the Fe70Pd30 films (10μm thickness) on PZT were deposited by sputtering method, exhibited 8 V at Hac of 175Oe, which is larger than 7.16 V for Fe76Ga17Co7 (50μm)/PZT/ Fe76Ga17Co7 (50μm) composites