【摘要】：釹鐵硼納米雙相永磁材料是一種綜合性能優(yōu)異的新型磁性材料,非晶晶化法是這種永磁材料的一種主要制備方法。然而由于Nd-Fe-B體系中亞穩(wěn)相較多且相變過程復(fù)雜,該體系的晶化過程尚未完全清楚。因此對該體系晶化過程的研究有著重要的意義。本論文研究了Nd2Fe14B/α-Fe, Nd2Fei4B/Fe3B兩種納米雙相永磁材料的晶化過程,及硼含量對晶化過程的影響。研究過程中對DSC曲線做了較深入的分析。探究了Nd2Fe14B/α-Fe體系中各相的形核長大規(guī)律以及快淬輪速與晶化過程的關(guān)系,并對其晶化工藝進(jìn)行了優(yōu)化。文中Nd2Fe14B/α-Fe型納米雙相永磁材料的母合金成分為Nd9Fe85Nb0.5B5.5, Nd2Fe14B/Fe3B型納米雙相永磁材料母合金成分為Nd9Fe78.5Nb0.5B 15,主要得到以下結(jié)論：(1)Nd9Fe8.5Nb0.5B5.5體系在18-24m/s輪速下制備的快淬合金晶化過程可以簡述為兩步：(Ⅰ) TbCu7型亞穩(wěn)相和少量的α-Fe從母合金中析出。(Ⅱ)TbCu7型亞穩(wěn)相分解為α-Fe和Nd2Fe14B相,兩相均勻分布。(2)Nd9Fe85Nb0.5B5.5體系α-Fe和Nd2Fe14B相兩相晶化機(jī)理不同,a-Fe滿足JMA(Johnson-Mehl-Avrami)推廣后的非等溫晶化模型,Nd2Fe14B相滿足SB(Sestak-Berggren)晶化模型,且Nd2Fe14B相的晶化過程為自催化反應(yīng)過程。(3)Nd9Fe8.5Nb0.5B5.5體系中,不同輪速下的快淬薄帶晶化過程有所不同,低輪速時Nd2Fe17Bx先從非晶母相中析出,接著分解為Nd2Fe14B相；當(dāng)輪速高于30m/s時Nd2Fe14B相和a-Fe直接從非晶母相中析出,并非Nd2Fe14Bx先析出再分解。不同輪速導(dǎo)致快淬合金初始相結(jié)構(gòu)有所不同,從而影響晶化過程。(4)Nd9Fe8.5Nb0.5B5.5體系最佳制備工藝,24m/s快淬輪速制備的薄帶在730℃條件下晶化4min所得的性能為最佳。[BH)max=10.96MGOe,Br=8.36kGs,Hcj=7.75kOe。而對于高輪速(30m/s以上)條件下制備的薄帶通過晶化很難得到磁性能較高的納米雙相材料,因?yàn)橹苯訌姆蔷е形龀鲇泊畔郚d2Fe14B和軟磁相α-Fe可能導(dǎo)致兩相分布不均勻。(5)合金成分中硼含量變化,晶化過程及析出相有所不同。晶化過程開始階段都會有α-Fe和Nd2Fe14B析出,非晶母相中形成富硼團(tuán)簇,根據(jù)合金成分不同,導(dǎo)致晶化過程中析出不同的相,Nd9Fe78.5Nb0.5B12成分的母合金中先析出的a-Fe晶粒不再生長,而是出現(xiàn)Oswald熟化現(xiàn)象機(jī)制,即小的納米晶a-Fe被大晶�！俺缘簟�。硼含量高的母合金Nd9Fe75.5Nb0.5B15晶化過程有Fe23B6和Nd2Fe23B3亞穩(wěn)相析出。晶化溫度升高Nd2Fe23B3分解為α-Fe, FesB及Nd1.1Fe4B4。
[Abstract]:NdFeB nanocrystalline permanent magnet is a new type of magnetic material with excellent comprehensive properties. The amorphous method is one of the main preparation methods of NdFeB nanomaterials. However, the crystallization process of Nd-Fe-B system is not completely clear due to its more metastable phases and complex phase transition process. Therefore, it is of great significance to study the crystallization process of the system. In this paper, the crystallization process of Nd2Fe14B/ 偽 -Fe, Nd2Fei4B/Fe3B nanocrystalline dual phase permanent magnetic materials and the effect of boron content on the crystallization process have been studied. In the course of the research, the DSC curve is analyzed deeply. The nucleation and growth law of each phase in Nd2Fe14B/ 偽 -Fe system and the relationship between the rapid quenching wheel velocity and the crystallization process were investigated, and the crystallization process was optimized. In this paper, the parent alloy composition of Nd2Fe14B/ 偽 -Fe nano-duplex permanent magnet is Nd9Fe85Nb0.5B5.5 and that of Nd2Fe14B/Fe3B nano-duplex permanent magnet is Nd9Fe78.5Nb0.5B 15. The main conclusions are as follows: (1) Crystallization process of quenched alloy prepared by Nd9Fe8.5Nb0.5B5.5 system at 18-24m/s wheel speed can be briefly described. (I) TbCu7 metastable phase and a small amount of 偽 -Fe precipitated from the master alloy. (II) the TbCu7 metastable phase was decomposed into 偽 -Fe and Nd2Fe14B phases. (2) the crystallization mechanism of 偽 -Fe and Nd2Fe14B phases in Nd9Fe85Nb0.5B5.5 system is different. The non-isothermal crystallization model of Nd2Fe14B phase satisfies the SB (Sestak-Berggren) crystallization model after the extension of JMA (Johnson-Mehl-Avrami), and the crystallization process of Nd2Fe14B phase is self-catalytic reaction process. (3) in Nd9Fe8.5Nb0.5B5.5 system, the crystallization process of Nd2Fe14B phase is self-catalytic. The crystallization process of the quenched strip is different at different wheel speeds. At low wheel speed, Nd2Fe17Bx precipitates from the amorphous parent phase and then decomposes into Nd2Fe14B phase, and when the wheel speed is higher than 30m/s, the Nd2Fe14B phase and a-Fe precipitate directly from the amorphous parent phase, not the Nd2Fe14Bx precipitate first and then decompose. The initial phase structure of the quenched alloy is different at different wheel speeds, which affects the crystallization process. (4) the best preparation process of the Nd9Fe8.5Nb0.5B5.5 system is 24m / s rapid-quenched ribbons prepared at 730 鈩，

本文編號：2185323