Papers by Author: Yasubumi Furuya

Abstract: Microstructures of the Fe-29.6at%Pd alloy ribbons were observed with an X-ray diffractometer and a transmission electron microscope. The X-ray diffraction profiles at room temperature showed that the ribbon consists of FCT martensitic phase and FCC parent phase. Moreover, the ribbon exhibits a strongly 200-oriented texture analyzing with pole figure measurements. TEM bright field images for the cross section of the ribbon showed high-density striation in the FCT martensite variants. Twin-related two sets of reflections were observed in the SAED patterns taken of the FCT martensite variants. _FCT was nearly parallel to the thickness direction according to the analysis of the SAED patterns. This result corresponds to the pole figure measurements.

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

Abstract: It is well known that FePd alloys are effective as a magneto-thermoelastic actuator material, because they have large magnetostriction and shape memory effect. In order to use the alloys for a micro-actuator, magnetic properties and microstructures have been examined as for rapidly solidified Fe-29.6 at% Pd alloy ribbons. The ribbons exhibit a large magnetostriction at room temperature and good shape memory effect. Magnetostriction and coercive force of the ribbons markedly depend on the direction of the applied magnetic field. Maximum values of magnetostriction and coercive force are obtained at θ = 85 degree (θ is the angle between the magnetic field and the ribbon plane). Relief effects corresponding to the formation of FCT martensite variants are observed on the grains. X-ray diffraction profile at room temperature shows that FCT martensitic phase and FCC parent phase coexist in the ribbon. Dense striations are observed in the TEM bright field images of FCT martensite plates. Selected area electron diffraction patterns revealed the striations to be thin twins.

Abstract: Technical importance of multi-ferroic approach for designing advanced multi-functional actuator/sensors based on a mutual coupling effect between ferroic material elements is pointed out for intelligent/smart technology. Two types of multi-ferroic actuator/sensor devices. i.e. (1) magnetically driven composite actuator and (2) multi-functional surface acoustic wave (SAW) sensor by MEMS are presented. First, a large-scale robust composite actuator is the composite structure which is reinforced by the superelastic fiber or lamellar of shape memory alloys (TiNi) in the ferromagnetic metal (Ni) matrix. This multi-ferroic composite can be driven with high speed as well as considerably enhanced strain by applying a wireless magnetic field. Secondarily, multi-functionally designed, multi-ferroic senor device using surface acoustic wave (SAW) is introduced. On the surface part between IDTs, environmentally active material films such as SMA, FSMA, magnetostrictive alloy etc. are formed by magnetron-sputtering. Various environmental sensing parameters i.e. temperature, magnetic field strength, stress, loading hysteresis and internal damage etc. can be evaluated nondestructively from the signal analysis of amplitude and phase change of SAW. Consequently, these results show the promising new types of multi-functional composite actuator and sensor based on multi-ferroic effect.

Abstract: In this paper, the TiNi fiber reinforced / Polycarbonate(PC) composite material is developed, and its properties is studied. Conducting fatigue experiments, shape memory effect of the material for preventing fatigue crack growth are investigated. The fatigue behavior and crack propagation are observed under increasing temperature with a SEM servo-pulser, which is a fatigue testing instrument with scanning electron microscope. As the results, the effectiveness of fatigue resistance is confirmed. The shape memory effect and expansion behavior of the matrix caused by increasing temperature create the effect of the fatigue crack propagation control. It is verified that the controlling of fatigue crack growth is attributed to the compressive stress field in the matrix which is caused by shrinkage of the TiNi fibers above austenitic finishing temperature (Af).