退火工艺对Finemet纳米合金磁性能的影响

Affection of thermal treatment on magnetism for Finemet nano-alloy

为改善Finemet合金的磁性能,通过氩气退火和横、纵磁应力退火对合金进行热处理,研究退火工艺对合金磁性能及微观结构、形貌的影响.使用LCR数字电桥法、共地三电压法及冲击法测试磁性能,利用场发射扫描电镜观察Finemet合金的非晶、纳米晶形貌,采用X射线仪分析Finemet合金的结构.研究表明,540℃氩气退火使合金的初始导磁率μi达最高值且矫顽力H c最低,非晶基体出现bccα-Fe(Si)纳米晶颗粒,580℃氩气退火使纳米晶数量和尺寸增加,磁性能下降;540℃横磁退火可获得狭长扁平的磁滞回线、低剩磁比Br/Bs和铁损P c,540℃纵磁退火可获得矩形磁滞回线、高Br/Bs和P c,横、纵磁退火均使μi和H c降低.因此,合理的退火工艺可优化Finemet合金磁性能,以适应不同的应用领域.

To improve magnetic performances of Finemet alloy, annealing in Ar, transversal and longitudinal magnetic stress annealing were used for the alloy to study the effect of annealing on magnetic properties, microscopic structure and morphology. Magnetic performances were tested by the methods of LCR digital bridge, three of the voltage, and impact, microstrueture was measured by XRD, amorphous-nanocrystalline morphology of Finemet alloy was investigated by FESEM. The results show that after annealing in Ar at 540 ℃, /xi reaches the highest and Hc is minimum, and bcc ot-Fe （Si） nano-particles emerge on the amorphous matrix, but after annealing in Ar at 580 ℃, the number and size of nano-particles are both increased and magnetic properties are decreased. Narrow and flat hysteresis, low values of Br/Bs and Pc are achieved by transversal magnetic annealing at 540 ℃ , rectangular hysteresis, high values of Br/Bs and Po are obtained by longitudinal magnetic annealing at 540 ℃, and transversal and longitudinal magnetic annealing at 540 ℃ can reduce the values of μi and Hc. So appropriate annealing processes can optimize the magnetic performances of Finemet alloy to meet different applications.