文章信息/Info

Title:

Control of Microstructure and Magnetic Properties of Nanocomposite Magnets

作者:

張湘義

亞穩(wěn)材料制備技術與科學國家重點實驗室，燕山大學

Author(s):

 Zhang Xiangyi' target="_blank" rel="external">"sans-serif"; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋體; mso-fareast-theme-font: minor-fareast; mso-hansi-theme-font: minor-latin; mso-bidi-font-size: 11.0pt; mso-bidi-font-family: "Times New Roman"; mso-bidi-theme-font: minor-bidi; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">Zhang Xiangyi

State Key Laboratory of Metastable Materials Science and Technology, Yanshan University

關鍵詞:

納米晶復合永磁材料; 納米晶; 微結構; 界面; 晶體取向; 嚴重塑性變形; 高壓

DOI:

10.7502/j.issn.1674-3962.2015.11.05

文獻標志碼:

A

摘要:

納米晶復合永磁材料因具有潛在的高磁能積，是頗具發(fā)展前途的下一代永磁材料。微結構控制是其獲得高磁能積的關鍵。本文總結和評述了我們在納米晶復合永磁材料微結構控制研究方面的主要結果。Nd-Fe-B非晶合金相變動力學研究結果表明，α-Fe軟磁相晶粒尺寸粗大（20-100 nm）且不均勻的物理根源是它的成核激活能（En）高和生長激活能（Eg）低，即軟磁納米晶難成核卻易生長（Eg /En < 1）；軟、硬磁納米晶的生長主要依靠熱空位協(xié)助原子的擴散來完成，F(xiàn)e原子的擴散控制著α-Fe納米晶的生長。室溫嚴重塑性變形可有效地控制軟、硬磁納米晶的尺寸（10-20 nm），抑制亞穩(wěn)相的形成，并獲得高體積分數（> 30%）的軟磁相。溫度梯度、高壓和高應力熱變形能促進永磁相Nd2Fe14B納米晶的易軸對中（取向），獲得各向異性納米晶永磁材料。調控軟、硬磁納米晶的界面結構和化學可以促進納米晶間磁交換耦合的增強和磁體矯頑力的提高。

Abstract:

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, yielding anisotropic α-Fe/Nd2Fe14B nanocomposite magnets. The exchange-coupling strength between soft and hard phase grains and the coercivity of magnets can be enhanced through the modification of interfacial structure and chemistry.
Keywords: Nanocomposite permanent magnets; Nanocrystals; Microstructure; Interface; Crystal orientation; Severe plastic deformation; High pressure.