纳米晶复合永磁材料的结构控制和性能研究  

Control of Microstructure and Magnetic Properties of Nanocomposite Magnets

作　　者：张湘义[1] 

机构地区：[1]亚稳材料制备技术与科学国家重点实验室,燕山大学,河北秦皇岛066004

出　　处：《中国材料进展》2015年第11期829-840,共12页Materials China

基　　金：国家自然科学基金资助项目(51471144;51471145;51371074)

摘　　要：纳米晶复合永磁材料因具有潜在的高磁能积，是颇具发展前途的下一代永磁材料。微结构控制是其获得高磁能积的关键。总结和评述了作者课题组在纳米晶复合永磁材料微结构控制研究方面的主要结果。Nd—Fe-B非晶合金相变动力学研究结果表明，α-Fe软磁相晶粒尺寸粗大（20～100nm）且不均匀的物理根源是它的成核激活能（En）高和生长激活能（Eg）低，即软磁纳米晶难成核却易生长（Eg／En〈1）；软、硬磁纳米晶的生长主要依靠热空位协助原子的扩散来完成，Fe原子的扩散控制着α-Fe纳米晶的生长。室温严重塑性变形可有效地控制软、硬磁纳米晶的尺寸（10～20nm），抑制亚稳相的形成，并获得高体积分数（〉30％）的软磁相。温度梯度、高压和高应力热变形能促进永磁相Nd2Fe14B纳米晶的易轴对中（取向），获得各向异性纳米晶永磁材料。调控软、硬磁纳米晶的界面结构和化学可以促进纳米晶问磁交换耦合的增强和磁体矫顽力的提高。Nanocomposite exchange coupled magnets are most likely next-generation magnets because of their potentially high energy products. Microstructural control is the key to achieve high energy products. This paper reviews our studies on microstructural control of nanocomposite magnets. The study of the kinetics of phase transition in amorphous Nd-Fe-B demonstrates that the mechanism underlying the coarse grain size （20 - 100 nm） of α-Fe phase in nanocomposite magnets is a high nucleation activation energy （En） and a low growth activation energy （Eg） , that is, the difficult nucleation and easy growth processes of the α-Fe phase, Eg/En 〈 1. The growth process of soft and hard phases is dependent on atomic diffusion mediated by vacancy-type thermal defects, in which the growth of α-Fe grains in size is dominantly controlled by the diffusion of Fe atoms mediated by thermal vacancies. Room-temperature severe plastic deformation （SPD） affects the grain size （10 ～ 20 nm） and volume fraction of soft phase significantly and inhibits the formation of metastable intermediate phases in the alloy. Temperature gradient, high pressure and hot deformation at high stress can induce the easy-axis alignment of Nd2Fe14B hard-phase grains, obtaining anisotropic a-Fe/Nd2Fel4B nanocomposite magnets. The exchangecoupling strength between soft and hard phase grains and the coercivity of magnets can be enhanced through the modification of interfacial structure and chemistry.

关 键 词：纳米晶复合永磁材料 纳米晶 微结构 界面 晶体取向 严重塑性变形 高压 

分 类 号：TM237[一般工业技术—材料科学与工程]