EFFECTS OF Ce ADDITION ON THE MICROSTRUCTURE AND MAGNETOSTRICTION OF Fe 83 Ga 17 ALLOY

Abstract

Fe-Ga alloy,which was a new type of magnetostrictive material with high magnetostriction, low hysteresis,high tensile strength and good machinability,has been widely studied. However,the magnetostrictive properties of the practically prepared Fe-Ga alloys were quite small at present.In order to improve magnetostrictive properties of the Fe-Ga alloy,the Fe_(83)Ga_(17)Ce_x(x=0.0, 0.2,0.4,0.6,0.8,1.0) alloys were prepared by non-consumable vacuum arc melting furnace using high purity elements under a protective argon atmosphere.The crystal structures and surface morphologies of the alloys were intensively studied by X-ray diffraction(XRD) and scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy(EDS),respectively.The magnetostriction coefficients of the alloys were measured by means of the resistance strain method.The results showed that Fe_(83)Ga_(17) alloy is composed only of a single phase of A2 with bcc structure.However,the Fe_(83)Ga_(17)Ce_x alloys are composed of the A2 phase and a small amount of CeFe_2 secondary phase with MgCu_2 structure except the alloy with x=0.2,which is composed only of a single phase of A2.Furthermore, the microstructure of the Fe_(83)Ga_(17) alloy presents the equiaxial morphology with coarse grains.However, the microstructure of the Fe_(83)Ga_(17)Ce_(0.8) alloy is a columnar structure with fine grains.Compared with the Fe_(83)Ga_(17) alloy,the magnetostriction coefficients of the Fe_(83)Ga_(17)Ce_x alloys are increased significantly except the alloy with x=0.2.The magnetostriction coefficient of the Fe_(83)Ga_(17)Ce_(0.2) alloy (81×l0~(-6)) is slightly smaller than that of the Fe_(83)Ga_(17) alloy(84xl0~(-6)).With the increase of the rare earth Ce content,the magnetostriction coefficients of the Fe_(83)Ga_(17)Ce_x alloys increase firstly and then decrease.When x=0.8,the maximum magnetostriction coefficient of 356×l0~(-6) is obtained at the magnetic field of 557 kA/m.For the Fe_(83)Ga_(17)Ce_x alloys except the alloy with x=0.2,the noticeable increase of the magnetostriction coefficients derives from the following reasons:(1) the secondary phase of CeFe_2 with MgCu_2 structure appears and increases with the increase of the rare earth Ce content in the alloys.(2) the preferred orientation along(100) of A2 phase of the Fe_(83)Ga_(17)Ce_x alloy is more favorable to the increase of magnetostriction coefficient of Fe-Ga alloy.As for the Fe_(83)Ga_(17)Ce_(0.2) alloy, the decrease of magnetostriction coefficient is attributed to the fact that the rare earth Ce dissolves in the Fe-Ga alloy and forms the solid solution alloy.