Combinatorial Investigation of Magnetostriction in Fe-Fa and Fe-Ga-Al

A high-throughput high-sensitivity optical technique for measuringmagnetostriction of thin-film composition-spread samples has been developed. It determines the magnetostriction by measuring the induced deflection of micromachined cantilever unimorph samples. Magnetostrictionmeasurements have been performed on as-deposited Fe–Ga and Fe–Ga–Al thin-film composition spreads. The thin-film Fe–Ga spreads display a similar compositional variation of magnetostriction as bulk. A previously undiscovered peak in magnetostriction at low Ga content was also observed and attributed to a maximum in the magnetocrystalline anisotropy. Magnetostrictive mapping of the Fe–Ga–Al ternary system reveals the possibility of substituting up to 8at.%Al in Fe70Ga30 without significant degradation of magnetostriction

Developments of new thermo-and magneto-elastic metallic sensor/actuator materials by controlling microstructures by rapid-solidification

The purposes of this study are to develop fine fiber and foil-type sensor/actuator material elements byusing the originally designed rapid solidification apparatus, and to investigate how to control the microstructures to prepare new multi-functional solid-state metallic sensor/actuator materials. By changing the rotating speed of rapidsolidification roller of either plane surface type or triangle-tip type, the thin foil or fine fiber sensor/actuator material elements can be produced. As the thermoelastic shape memory alloy (TSMA), sharp and non-linear hysteresis TiNiCu and linear and little-hysteresis TiNiCo, both of which function at room temperature range, were developed. As the ferromagnetic shape memory alloy (FSMA), FePd, FePt and CoNiGa with improvement of their ductility have been developed. The magnetostriction in rapid-solidified Fe-29.6at%Pd foil with strong texture of (100) crystal orientation showed 1200 x 10-6 (= 1200 ppm) strain which is about 40 times larger than that of randomly oriented polycrystalline material. By the same production method, we got very high magnetostriction (400 ppm) and very high ductility (i.e. 180° bending is possible) in Fe-15at%Ga foil

Heihachi Shimada Local Crack-Tip Strain Concept for Fatigue Crack Initiation and Propagation

Introduction (I) Background. Fatigue is characterized by the very local and cyclic fracture. In order to make clear the phenomena of fatigue and the various problems of these stages, we have been studying the local deformation behaviors at the notch-root for crack initiation and the tip of propagating crack by using realtime fine-grid method We have shown the next two main results. (i) Fatigue crack initiation was controlled by local-strain damage accumulation. For a quantitative expression of cumulative fatigue damage, we showed "local strain damage accumulation curve (Ae, versus N c relation), and "linear cumulative damage law" based on Ae, value (ii) Fatigue crack propagation rate (da/dN) could be successfully expressed by our proposed parameter, "local cracktip strain range" in the wide range from "small" to "large" fatigue crack Concerning the total fatigue life estimation method, up to the present, two parameters approach (i.e., gross-strain based Manson-Coffin type relation, Ae, versus N n and macroscopic fracture mechanics, AK) has been generally discussed due to the qualitative and phenomenological differences between the two processes, crack initiation and propagation However, if our attention is focused on the "local" notchroot or crack-tip region where the cyclic fracture are processing, the authors would like to believe the possibility that crac

Detectability of stress-induced martensite phase in ferromagnetic shape memory alloy Fe-30.2at.%Pd by Barkhausen noise method

The possibility to detect the phase transformation of stress-induced martensite in ferromagnetic shape memory alloy Fe–30.2at.%Pd thin foil was investigated by using Barkhausen noise (BHN) method. Stress-induced martensite twin was observed by laser microscope above loading stress of 25 MPa. BHN caused by grain boundaries appears in the lower frequency range and BHN by martensite twin in the higher frequency range. The envelope of the BHN voltage as a function of time of magnetization shows a peak due to austenite phase at weak magnetic field. The BHN envelope due to martensite twins creates additional two peaks at intermediate magnetic field. BHN method turns out to be a powerful technique for non-destructive evaluation of the phase transformation of ferromagnetic shape memory alloy