Xing Mu

Electromagnetic induced voltage signal to magnetic variation through torquing textured Fe81Ga19 alloy

The results of a study on the suitability of Fe-Ga alloys for torque sensor applications are presented. A Fe81Ga19 rod with a ⟨100⟩ preferred orientation along the length direction is prepared for the torque shaft and as the electromagnetic induction sensitive element, which is wound with three coils for signal excitation, signal pickup, and applied bias magnetic field, respectively. An apparent decrease in the induced voltage signal (peak voltage) of 3.88 mV is observed as the torque loading is 50 N m in the presence of a sine excitation signal (10 V, 1 kHz) and a bias current of 0.5 A. Meanwhile, a good repeatability and stress sensitivity are obtained, especially in the low torque range. These behaviors stem from the stress induced decrease in the magnetic permeability and the rotation of the arranged magnetic moment. Here, we use the Fe81Ga19 alloy as the shaft material; nevertheless, in practical use, the same effect can be achieved by forming a Fe-Ga layer with large magnetostriction on the surface ...

Magnetic Domain Motion and Magnetostriction in the Fe–Ga Sheets

The magnetic domain motion with varying magnetic field is investigated by magneto-optic Kerr microscopy on a slightly Goss misoriented Fe-Ga rolled sheet, and a close relationship between the magnetostriction and the domain motion is reported during the magnetization process. Along the rolling direction (RD), a high magnetostriction value λ// of 281 ppm is observed under no prestress for the sheet. The magnetic domains on the ~12° misoriented Fe-Ga (110) surface appear in the lancet shape and align as lancet comb structures. The lancet domain motion on the surface well explains the magnetostrictive performance λ// with the consideration of 90° domains within the lancet structure. The rapid increase of magnetostriction is attributed to the quick motion of 90° domains within the lancet structure under the field below 70~100 Oe. Under the higher magnetic field, these lancet domains gradually disappear with the field increasing, accompanied with the approach to the saturation magnetostriction along the RD.

Temperature and magnetic field dependencies of the Young's modulus in magnetostrictive Fe-Ga alloys

Anomalous temperature dependences of Youngs modulus were observed in the as-cast and directionally solidified Fe100-xGax alloys (x = 20, 22, 24, 27). However, the absence of the anomalous temperature dependence of Youngs modulus in the DO19 and L12 ordered Fe73Ga27 alloys revealed that the anomalous temperature dependences of Youngs modulus of Fe-Ga alloys with different structures were only related with the structure transformation during the heating process. The relationship between the variations of Youngs modulus and structural transformation in the Fe78Ga22 alloy indicated that the lattice shrinkage owing to the structural transformations of A2 → DO3 and BCC(A2/DO3) → L12 was offset by the lattice expansion of the A2 phase caused by the thermal effect, which lead to a near constant coefficient of Youngs modulus in the temperature range from 500 °C to 560 °C. In addition, the variability of Youngs modulus as high as 12.8% was obtained in the as-directional solidified Fe73Ga27 alloy.

Enhancement of ductility and improvement of abnormal Goss grain growth of magnetostrictive Fe–Ga rolled alloys

The influences of initial microstructures on the mechanical properties and the recrystallization texture of magnetostrictive 0.1at% NbC-doped Fe83Ga17 alloys were investigated. The directionally solidified columnar-grained structure substantially enhanced the tensile elongation at intermediate temperatures by suppressing fracture along the transverse boundaries. Compared with tensile elongations of 1.0% at 300°C and 12.0% at 500°C of the hot-forged equiaxed-grained alloys, the columnar-grained alloys exhibited substantially increased tensile elongations of 21.6% at 300°C and 46.6% at 500°C. In the slabs for rolling, the introduction of <001>-oriented columnar grains also promotes the secondary recrystallization of Goss grains in the finally annealed sheets, resulting in an improvement of the saturation magnetostriction. For the columnar-grained specimens, the inhomogeneous microstructure and disadvantage in number and size of Goss grains are improved in the primarily annealed sheets, which is beneficial to the abnormal growth of Goss grains during the final annealing process.