Effect Of Mechanical Properties And Annealing On The Electromagnetic Performance Of Glass-coated Amorphous Microwires

In recent years, with the rapid development of high technology, excellent softmagnetic materials are needed to promote technological innovation to meet therequirements of the sensor accuracy and sensitivity of magnetic components. Because ofthe excellent electromagnetic and mechanical properties, the amorphous wire gets awide range of application prospects in automotive, computer, power electronics,bio-medicine and other fields. Especially, more attention has been paid to glass-coatedwires because they have good corrosion resistance and mature industrialized preparationconditions.A summary of research on amorphous wire and giant magneto-impedance effect ispresented in the thesis. Amorphous co-based microwires were prepared by theglass-coated method. The mechanical properties of the amorphous co-based microwiresand the affect after vacuum annealing were studied. The main study focuses on theaffect of the electromagnetic properties in cobalt-based glass-coated wires after beingtreated by different excitation current frequency and annealing conditions. The maincontent is listed as followed:First, Co₆₇Fe₄Si₁₅B₁₁Ni_1.5Cu_1.5was prepared by glass-coated method. We chose thetemperatures were350℃,450℃and500℃to take vacuum annealing in20minutesholding time to the amorphous wire which contains50μm diameter of core metal and80μm outer diameter. And then, tensile tests were taken to the prepared and annealedamorphous wire at the room temperature. The results showed that the preparedcobalt-based amorphous wire, which has the fracture form of brittle fracture, and has ahigh tensile strength, low elongation and no macroscopic plastic deformation. As theannealing temperature increased, the tensile strength and elongation of the amorphouswire were reduced, while the modulus of elasticity was slightly increased.Then, vibrating sample magnetometer were used to measure the hysteresis loop ofcobalt-based amorphous wire. It showed that the prepared cobalt-based amorphous wirewith magnetic anisotropy had a low hysteresis loop coercivity and remanence. The giantmagneto-impedance effect under different excitation current frequency of the preparedamorphous wire was obtained from the impedance analyzer. Combined with thetheoretical analysis, it was found the amorphous wire only contained magneticinductance effect and small impedance changed at low frequency, thus the ring magnetic permeability was mainly due to the movement of magnetic domain. At higherfrequency, ring permeability mainly caused by the rotation of magnetic moment becauseof the common role of the skin effect and eddy current. With the increase of impedancechange rate, a characteristic frequency at the maximum impedance change rate can beobtained.At last, the time was chosen as1,2and3min to take direct-current annealing at80mA to the amorphous wire which contained50μm diameter of core metal and80μmouter diameter. The changes of external magnetic field and the response to magneticfield sensitivity were studied. The results showed that different annealing methods couldvary improve the giant magneto-impedance effect of amorphous wire. Vacuumannealing can effectively improve the affect to magnetic field response sensitivitycausing by giant magneto-impedance effect of amorphous wire. Otherwisedirect-current annealing had no effect actually.