Study On Soft Magnetic And Pizeomagnetic Property Of Fe-based Amorphous Nanocrystalline Ribbons With A Tiny Amounts Of La

In this paper, trace amounts of La added to Fe-based amorphous ribbons of FeSiB and FeCuNbSiB were successfully prepared by single-roller quenching method. The glass forming ability and the structure of amorphous strips were detected by means of X-ray diffraction (XRD), differential thermal analysis (DTA, DSC). The effects of the factors such as annealing process and the packaging materials on the Static DC and Dynamic AC soft magnetic property of amorphous strips were studied. Then the influence of test frequency, test temperature and annealing temperature on the piezomagnetic property of amorphous strips were investigated.The results show that the glass forming ability of it will improve when it adds trace of La to FeSiB amorphous strips, and the precipitating of Fe-Si and Fe-B phase will also be blocked, thus the thermal stability of amorphous strips will increase. But as far as that the thermal stability of FeCuNbSiB amorphous strips after adding trace of La decreases because of the descending of the crystallizating temperature of Fe-Si phase, moreover its glass forming ability also decreases due to the exist of La.The DC and AC soft magnetic property of Fe-based amorphous strips significantly improve after annealing treating, especially above 300℃of the annealing temperature, the initial permeability(μi), maximum permeability(μm), saturation induction density(Bs), residual magnetic flux density(Br), effective magnetic permeability(μe), quality factor(Q) dramatically increase and the coercive force (Hc), iron loss(Pu) rapidly decrease as soon as the increasing of annealing temperature. The best annealing process of FeSiB-La strips is 400℃for 120 min, its crystallization phase is Fe0.9Si0.1 with BCC structure. But the best annealing process of FeCuNbSiB-La strips is 500℃for 120 min, its crystallization phase is Fe3Si with FCC and BCC structure. The soft magnetic property of the ribbons dramatically decreases as soon as excessively high annealing temperature, the devil of it will become to constant permeable alloy. In addition, the soft magnetic property of strips also will decrease when the content of La is too higher. Furtherore theμe gradually decrease and the Q firstly increase and then decrease with the rising of test frequency, and its center frequency is nearby 40 KHz. Moreover, the hard materials is better then the soft materials when packaging to magnetic core.Further more, the results show that the La not only affect the soft magnetic property of amorphous strips, but also its piezomagnetic property. The stress impedance ratio (SI%) of FeSiB amorphous strips decrease with the addition of La. But to FeCuNbSiB amorphous strips, its SI% increase after adding La to the strips. The SI% of the ribbons increase with the rising of test frequency in the range of 1 KHz-l MHz, and the frequency of its maximum SI% gradually increases with the content of La increasing. Under the same conditions, the SI% of Fe-based amorphous strips firstly dramaticlly increase to negative direction and then trend to stable. In addition, there both have a sensitive area of stress in these amorphous strips, its scope width will become narrow when adding trace of La. the scope of FeSiB strips is from 0-0.4 MPa to 0-0.2 MPa, but the scope of FeCuNbSiB strips is from 0-0.3 MPa to 0-0.2 MPa. The SI% of amorphous ribbons is to maximum at 40℃of test temperature, and the temperature drift instability of stress impedance effect of amorphous strips will get better just at the La addition on amorphous strips. The SI effect of strips dramatically improves during annealing at the right temperature, and the best annealing temperature of the pure FeSiB strips is 200℃, the best annealing temperature of the pure FeCuNbSiB strips is 300℃. But the SI% of it suddenly increases at 400℃of annealing temperature when it adds small amounts of La.