An In Situ Investigation On The Mechanism Of Magnetic Anisotropy Induced In Fe-Based Ribbons During Stress Annealing

The mechanism of stress induced magnetic anisotropy is an important basic science problem which has been investigated extensively. Limited by Static observation technology, currently, the understanding about the mechanism of stress induced magnetic anisotropy still exists disputes. Using in-situ observation technology, this paper studies the dynamic process that Fe73.sCu1Nb3Si13.5B9 alloy ribbon (Fe-based alloy ribbon) prepared with single roll faster quenching is under the effect of stress that current annealing (current stress annealing) induced magnetic anisotropy. We design a device which can monitor in-situ the length variation of Fe-based alloy ribbon during current stress annealing process and give a tracking measurement in-situ to the elongation of ribbon which is on the whole process of current stress annealing. Besides, We design a synchrotron radiation monitoring in-situ device and monitors in-situ the interior microcosmic structure of ribbon on annealing process by using Shanghai Synchrotron Radiation Facility (SSRF) BL15U —Hard X-ray micro focus and applied the beam line station. Using HP4294A type impedance analyzer to test the magnetic anisotropy field induced by stress annealing ribbon, we finally analyze and discuss the mechanism of stress annealing induced magnetic anisotropy. The research results are as follows:一、the flexibility of Fe-based alloy ribbon during the process of current stress annealing and tempering1. When it is small stress annealing (<5MPa), the length of Fe-based alloy ribbon contracts and magnetic anisotropy decreases.2. During current stress annealing process, when annealing current increases from 0 to 20A/mm2, the length of Fe-based alloy ribbon elongates linearly with the increase of annealing current square value, which is heat expansion; when annealing current is over 20A/mm2 is, the relationship of ribbon’ length and annealing current square value is not linear, which is creep.3. magnetic anisotropy induced from current stress annealing of amorphous alloy ribbons (sample a) is bigger than that of nano-crystalline ribbons (sample b).4. the elongation of sample a is almost same to that of sample b when annealing current density J≤20A/mm2, while the elongation of sample a becomes bigger than that of sample b when J≥20A/mm2. At the same time, with the increasing of annealing current, the elongation difference increased in the process of sample a and sample b is big further. During J=32.83A/mm2 and heat preservation 20min, sample a’s elongation is 17.71mm, which is 44.28 times bigger than sample b’s (0.4mm); during temperature-fall period, sample a’s contraction is 0.93, which is 1.52 times bigger than that of sample b’s (0.61mm). When is in 445MPa stress, J=32.83A/mm2 and heat preservation 20min, we let ribbons annealing, lower temperature and then be indoor temperature, sample a’s final elongation (18.52mm) is 41.16 times bigger than that of sample b’s (0.45mm).5. When is in 445MPa stress, J=32.83A/mm2and heat preservation 20min, after annealing, tempering it 80min with J=32.83A/mm2, sample a contracts 0.62mm, and the contraction percentage of annealing elongation part is just 3.35%. When is in 445MPa stress, J=32.83A/mm2 and heat preservation 20min, after annealing, tempering it 20min with J=32.83A/mm2, sample b contracts 0.16mm, and the contraction percentage of annealing elongation part reaches 35.56%, the magnetic anisotropy field minishes 45%.二、The research of synchrotron radiation on current stress annealing process1.The crystal anisotropic can be induced by stress annealing, that is to say dp the interplanar crystal spacing paralleled to the stress direction (ribbon axial) is different from dv the interplanar crystal spacing which is vertical stress direction. Annealed with small stress(5MPa), the samples’interplanar crystal spacing of p and v are hardly different, dp≈dv.While with big stress (445MPa), the interplanar crystal spacing of p and v change clearly, Ad=0.01314 A.2. Giving 445MPa stress to sample b and increasing annealing current to 32.83A/mm2, during the temperature-rise period, when annealing current J≤20A/mm2. Δd ≈0.When J>20A/mm2, Ad present index variation with the increasing of annealing current.3. Giving 445MPa stress to sample a and increasing annealing current to 32.83A/mm2, there is no crystallization peak appears during the temperature-rise period. When crystallization peak appears, Δd=0.02566 A, and when unloading it after annealing, Δd=0.02159 A. If tempering it with 25MPa stress, we can find Ad of tempering accounts for 47.61% that Ad of annealing.4. When giving 445MPa stress to sample b and increasing annealing current to 32.83A/mm2, Δd=0.01314 A, and when unloading it after annealing, Δd=0.02159 A. If tempering it with 25MPa stress, we can find Ad of tempering accounts for 64.61% that Ad of annealing.三、the mechanism of magnetic anisotropy induced by stress annealingIn the process of stress annealing,the anelasticity produced by amorphous base creeping, leads to interplanar crystal spacing anisotropy and grain magnetic anisotropy. Interplanar crystal spacing anisotropy and grain magnetic anisotropy are the two factors of the magnetic anisotropy induced by stress annealing.