Magnetic Properties and Microstructures of Rapidly Solidified FePd Alloy Ribbons

Yoichi Kishi,Teiko Okazaki,Manfred Wuttig,Zenjiro Yajima,Yasubumi Furuya

doi:10.4028/www.scientific.net/ast.59.24

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.

Highlights

Ferromagnetic Shape Memory Alloys (FMSMAs) form a new class of functional materials, because they show ferromagnetic nature plus shape memory effect and pseudoelasticity
In our previous studies [6, 7], we reported that polycrystalline FePd FMSMA ribbons made by rapidly solidified melt-spinning showed a good ductility, strong crystal anisotropy, giant magnetostriction as well as shape memory effect
Relief effects corresponding to the formation of FCT martensite variants were observed on the surface of the crystal grains

Summary

Introduction

Ferromagnetic Shape Memory Alloys (FMSMAs) form a new class of functional materials, because they show ferromagnetic nature plus shape memory effect and pseudoelasticity. It has been reported that single crystals of ferromagnetic Ni2MnGa [1], FePd [2, 3] and FePt [4] alloys under a magnetic field cause a strain of a few percent by the re-arrangement of martensite variants [5]. These crystals are either expensive or brittle in manufacturing thin plate and/or wire actuators at present.

Experimental Procedure

Summary