Influence of rare earth element terbium doping on microstructure and magnetostrictive properties of Fe81Al19 alloy

Abstract

Fe81Al19Tbx (x=0, 0.05, 0.1, 0.2, 0.3, 0.4) alloys were prepared by a non-consumable vacuum arc melting technique under an inert argon gas atmosphere. The microstructures of the alloys were studied by X-ray diffraction (XRD) and scanning electron microscopy combined with an energy dispersive spectroscopy (SEM/EDS). The magnetic properties and magnetostriction coefficients of the alloys were measured by a vibrating sample magnetometer (VSM) and adifferential resistive strain sensor, respectively. The results show that the Fe81Al19 alloy consists of a single A2 phase with bcc structure, whereas the Tb doped Fe81Al19 alloys are composed of the A2 phase and a small amount of rare earth-rich phase. The doping of the rare earth element Tb makes the Fe81Al19 alloy preferentially oriented along with the <100> crystal direction. With the increase of Tb content, the magnetostriction coefficient of the alloy first increases and then decreases. When x=0.1, the magnetostriction coefficient reaches the maximum, which is 146 × 10−6. Compared with the as-cast Fe81Al19 alloy (27 × 10−6), it increases by 441%. The enhanced magnetostrictive properties are mainly attributed to the preferred orientation along <100> of A2 phase of the Tb doped Fe81Al19 alloys and lattice distortion caused by the small amount of rare earth atoms entering the Fe–Al alloy lattice.