高磁能积NdFeB永磁体的热退磁机理分析  

Study on thermal demagnetizing mechanisms of high-energy product NdFeB permanent magnet

作　　者：陈杰[1,2] 程玲莉[2] 张明[2] 徐光亮[1] 高旭山[2] 

机构地区：[1]西南科技大学材料科学与工程学院,四川绵阳621010 [2]西南应用磁学研究所,四川绵阳621000

出　　处：《磁性材料及器件》2012年第3期49-52,61,共5页Journal of Magnetic Materials and Devices

基　　金：国家重大科技专项(2008ZX01006-005)

摘　　要：对高磁能积NdFeB永磁体的热退磁机理进行了分析。首先测量并研究永磁体开路磁通随温度的宏观变化,然后采用多功能显微镜、热分析仪及X射线衍射仪观察了高温金相形貌并分析了物相和表面成分变化,借助磁力显微镜观察了磁畴结构,从而分析了永磁体的热退磁机理。高温金相观察结果表明,在320℃以内,除金相形貌的颜色发生变化外,晶粒形状及尺寸均未发生明显变化;XRD分析表明,金相形貌的颜色变化是表面氧化所致,说明磁体在320℃以内的热退磁现象与金相结构无关,即热退磁不是由金相结构变化引起的。320℃以后,XRD及高温金相分析表明表面氧化变严重,尤其在580℃时有富Nd相熔融物析出,晶界模糊、大晶粒吞并小晶粒,金相结构发生明显变化。但磁畴观察结果表明,320℃内热退磁前后磁化强度方向发生偏转,方向一致性变差,是热退磁的原因所在。The demagnetization mechanism of high energy product NdFeB permanent magnet was analyzed. Firstly, changes of open-circuit magnet flux with temperature were studied. And then high-temperature metallurgical phase as well as surface composition changes were observed and analyzed using multi-functional metallographic microscope, thermal analysis instrument and X-ray diffraction, respectively. Finally we studied the phase magnetic domain structure of sintered NdFeB permanent magnet after magnetization and high-temperature treatment using magnetic force microscopy （MFM）. The experimental results showed that in addition to changes in color of microstructure morphology, no obvious change occurs in grain shape and size below 320℃. XRD analysis showed that the color change is due to surface oxidation, which indicates that thermal demagnetization below 320℃ has nothing to do with the metallurgical structure. XRD and metallographic analysis also showed that surface oxidation becomes serious above 320℃, especially at 580℃ melting Nd-rich phase precipitates, the grain boundary became fuzzy and large grain annexes small one. However, magnetic domain observation showed that, magnetization direction changes after thermal demagnetization below 320℃, which is the fundamental reason for thermal demagnetization.

关 键 词：NDFEB磁体 热退磁 磁通 金相形貌 磁畴结构 

分 类 号：TM273[一般工业技术—材料科学与工程]