Stress torsional magneto-impedance effect and mechanical properties of Co-based metallic microfibers

GMI characteristics of Co-based metallic microfibers under different stresses are tested by stress torsional magneto-impedance comprehensive platform. The internal stress distribution of microfibers is simulated with ANSYS finite element software and the fracture mechanism is analyzed based on fracture morphology. The experimental results indicate that tensile stress can enhance the GMI effect of metallic microfibers, and the significant [ΔZ/Zmax]max of 293.63% at a frequency of 3 MHz is obtained under the tensile stress of 482 MPa. The simulation results demonstrate that the internal stress concentration occurs at clamping end under tensile stress, and which accumulating on the surface of microfibers after applying torsional strain, thus weakening GMI effect. The fracture morphology will change with external stress, some vein-shaped patterns and molten drops can be seen in the cross-section under tensile stress, and the helical vein-shaped patterns appear with the application of torsional strain. In addition, the circular domain wall energy will be increased due to magnetoelastic anisotropy has been affected by tensile stress, which promotes an increment of circular magnetic permeability, thus improving the GMI effect of microfibers. However, the appearance of helical anisotropy after torsional strain is added will weaken the circular domain wall energy.