1.College of Physics, Electronic and Information Engineering, Zhejiang Normal University, Jinhua 321004, China 2.Key Laboratory of Solid State Optoelectronic Devices of Zhejiang Povince, Zhejiang Normal University, Jinhua 321004, China 3.Tourism College of Zhejiang, Hangzhou 311231, China 4.College of Science and Technology, Xinjiang University, Akesu 843100, China
Fund Project:Project supported by the National Basic Research Program of China (Grant No. 2012CB825705), the Key Research Program of Zhejiang Province, China (Grant No. 2018C01G2031345), the Natural Science Foundation of Zhejiang Pvovince, China (Grant No. LY14A040003) and the National Natural Science Foundation of China (Grant No. 51771083).
Received Date:04 January 2019
Accepted Date:15 May 2019
Available Online:06 June 2019
Published Online:05 July 2019
Abstract:The magnetic properties of Fe-based alloy ribbons are sensitive to stress, and it’s an interesting scientific question whether stress-induced magnetic anisotropy during annealing procedure can be eliminated by tempering. In this paper, the synchrotron radiation technique was used to observe the microstructure of Fe73.5Cu1Nb3Si13.5B9 amorphous ribbons annealed at 540 ℃ for 30 minutes under 394.7MPa stress and tempered several times at the same temperature. The macroscopic elongation of the samples during stress annealing and tempering was recorded by SupereyesB011 microcamera, and the magnetic anisotropy of the samples was measured by HP4294A impedance analyzer. After fitting the experimental data, it is found that: (a) The lattice anisotropy, macroscopic strain and magnetic anisotropy of the sample show negative exponential attenuation with the tempering times, and their final residual are 19.04%. 98.27% and 31.65%. (b) Multiple tempering can not completely eliminate lattice anisotropy, macroscopic strain and magnetic anisotropy induced by stress annealing. (c) The magnetic anisotropy of the sample has a linear relationship with the lattice anisotropy, but the intercept between the reverse extension line of the relation curve and the longitudinal coordinate is not zero. When the lattice anisotropy is zero, there is still 16.36% magnetic anisotropy. This is different from Ohnuma's conclusion that lattice anisotropy is the direct cause of magnetic anisotropy. (d) The structure anisotropy caused by the residual stress after stress annealing is the main cause of magnetic anisotropy, but it is not the only reason. The directional congregation of agglomerated nanocrystalline grains caused by creep of amorphous substrates during stress annealing is also an important cause of magnetic anisotropy induced by stress annealing. Moreover, the magnetic anisotropy induced by the directional congregation of agglomerated nanocrystalline grains due to the creep of amorphous substrates during stress annealing can not be completely eliminated by tempering. Keywords:stress annealing/ tempering/ structure anisotropy/ magnetic anisotropy
从(9)式可见, 当$n \propto \infty $时, 薄带的残余宏观应变$\delta $随着回火次数的增加逐渐减小, 并最终趋近于98.27%. 图 3 Fe基合金薄带残余宏观应变与回火次数的关系曲线 Figure3. Relationship between the residual macroscopic strain and tempering times of the ribbon
其中${H_K}$为薄带的磁各向异性, 由(5)式算出, n为回火次数(n取0, 1, 2, 3, 4), n为0时代表未回火. 图5为合金薄带样品残余磁各向异性与回火次数的关系曲线, 未回火前薄带残余磁各向异性为100%, 每次回火之后其残余磁各向异性分别为42.54%, 35.76%, 31.76%和30.40%. 对图中实验数据点进行最小二乘法拟合后得到薄带残余磁各向异性与回火次数的关系式: 图 5 Fe基合金薄带残余磁各向异性与回火次数的关系曲线 Figure5. Relationship between the residual magnetic anisotropy and tempering times of the ribbon.
表1(7), (9)和(11)式的参数比较 Table1.Comparison of parameters between equation (7), (9) and (11).
图6为经应力退火的Fe基合金薄带多次等温回火过程中残余晶格各向异性和残余磁各向异性的关系曲线, 从右往左的两个数据点之间的间隔为一次等温回火, 从图中可以看出薄带的残余磁各向异性与残余晶格各向异性之间有较好的线性关系. 对图中实验数据点进行线性拟合后可以得到关系式 图 6 Fe基合金薄带残余磁各向异性与残余晶格各向异性的关系 Figure6. Relationship between the residual magnetic anisotropy and the residual structure anisotropy of the ribbon
图 1 经应力退火和回火的Fe基薄带的XRD谱
图 2 Fe基合金薄带残余晶格各向异性与回火次数的关系曲线
图 3 Fe基合金薄带残余宏观应变与回火次数的关系曲线
图 4 薄带应力退火和多次回火的GMI曲线
图 5 Fe基合金薄带残余磁各向异性与回火次数的关系曲线
图 6 Fe基合金薄带残余磁各向异性与残余晶格各向异性的关系