Fe_(72.5)Ga_(27.5)磁致伸缩合金动态机电耦合系数K_(33)

ELECTROMECHANICAL COUPLING COEFFICIENT (K_(33)) OF Fe_(72.5)Ga_(27.5)MAGNETOSTRICTIVE ALLOY

采用区熔定向凝固法制备目标成分为Fe_(72.5)Ga_(27.5)的磁致伸缩定向生长试样.采用改进的交流阻抗法测定定向生长态及其淬火态(1000℃/3 h,W.Q.)试样的阻抗谐振频率谱,求出不同偏振磁场和预压力情况下的动态机电耦合系数K_(33).由于Fe-Ga合金的磁致伸缩性能比Tb-Dy-Fe巨磁致伸缩材料小一个数量级,原有的测试方法不易得Fe-Ga合金的K_(33).本实验在拾取信号时采用了四线并接接线方式并将交流激励信号输入水平调整到0.5 A,获得了稳定且明显的Fe-Ga合金阻抗谐振频率谱线.实验结果表明:定向生长试样在32.7 mT偏振磁场、无预压应力下K_(33)为0.103;淬火态试样在同样偏振磁场和无预压应力下K_(33)达到0.137.K_(33)随外加偏振磁场的增大而减小,随预压力的增大呈现先增大而后减小的趋势.淬火态试样的K_(33)较定向生长试样有明显提高.外加偏振磁场和预压力对淬火态试样的K_(33)的影响规律同定向生长试样一致.

The electromechanical coupling coefficient （K33） is a crucial parameter to express the efficiency of the magnetostrictive alloy. Fe72.5Ga27.5 magnetostrictive oriented crystal has been prepared by zone melting unidirectional solidification. The K33 values of the directionally solidified sample and its quenched sample（1000 ℃/3 h, W. Q.） were determined by improved AC impedance resonance frequency testing method. The DC magnetic field was formed by the DC coil and the prepressure was given by the press-pack. Since the magnetostriction of Fe-Ga Alloy is less than that of the giant magnetostrictive material of Tb-Dy-Fe by 10 times, the K33 of Fe-Ga alloy cannot be determined by the traditional testing methods. In this paper, a 4-wire configuration connection was used to pickup the signal in experiment, and the AC excitation signal was adjusted to 0.5 A, so that the obvious and stable AC impedance curves of the Fe-Ga alloy were acquired. When the DC magnetic field is 32.7 mT and no compressive pre-stress is applied, the K33 values of the directionally solidified sample and quenched sample are 0.103 and 0.137, respectively. The K33 values of the two kinds of Fe72.5Ga27.5 magnetostrictive alloys decrease with increasing DC magnetic field, and increase at first then decrease with increasing pre-pressure, but the K33 value of the quenched sample always higher than that of the oriented sample.