Nd-Fe系非晶合金晶化机理研究
发布时间：2018-08-16 07:41
【摘要】：钕铁硼纳米双相永磁材料是一种综合性能优异的新型磁性材料,非晶晶化法是这种永磁材料的一种主要制备方法。然而由于Nd-Fe-B体系中亚稳相较多且相变过程复杂,该体系的晶化过程尚未完全清楚。因此对该体系晶化过程的研究有着重要的意义。本论文研究了Nd2Fe14B/α-Fe, Nd2Fei4B/Fe3B两种纳米双相永磁材料的晶化过程,及硼含量对晶化过程的影响。研究过程中对DSC曲线做了较深入的分析。探究了Nd2Fe14B/α-Fe体系中各相的形核长大规律以及快淬轮速与晶化过程的关系,并对其晶化工艺进行了优化。文中Nd2Fe14B/α-Fe型纳米双相永磁材料的母合金成分为Nd9Fe85Nb0.5B5.5, Nd2Fe14B/Fe3B型纳米双相永磁材料母合金成分为Nd9Fe78.5Nb0.5B 15,主要得到以下结论：(1)Nd9Fe8.5Nb0.5B5.5体系在18-24m/s轮速下制备的快淬合金晶化过程可以简述为两步：(Ⅰ) TbCu7型亚稳相和少量的α-Fe从母合金中析出。(Ⅱ)TbCu7型亚稳相分解为α-Fe和Nd2Fe14B相,两相均匀分布。(2)Nd9Fe85Nb0.5B5.5体系α-Fe和Nd2Fe14B相两相晶化机理不同,a-Fe满足JMA(Johnson-Mehl-Avrami)推广后的非等温晶化模型,Nd2Fe14B相满足SB(Sestak-Berggren)晶化模型,且Nd2Fe14B相的晶化过程为自催化反应过程。(3)Nd9Fe8.5Nb0.5B5.5体系中,不同轮速下的快淬薄带晶化过程有所不同,低轮速时Nd2Fe17Bx先从非晶母相中析出,接着分解为Nd2Fe14B相；当轮速高于30m/s时Nd2Fe14B相和a-Fe直接从非晶母相中析出,并非Nd2Fe14Bx先析出再分解。不同轮速导致快淬合金初始相结构有所不同,从而影响晶化过程。(4)Nd9Fe8.5Nb0.5B5.5体系最佳制备工艺,24m/s快淬轮速制备的薄带在730℃条件下晶化4min所得的性能为最佳。[BH)max=10.96MGOe,Br=8.36kGs,Hcj=7.75kOe。而对于高轮速(30m/s以上)条件下制备的薄带通过晶化很难得到磁性能较高的纳米双相材料,因为直接从非晶中析出硬磁相Nd2Fe14B和软磁相α-Fe可能导致两相分布不均匀。(5)合金成分中硼含量变化,晶化过程及析出相有所不同。晶化过程开始阶段都会有α-Fe和Nd2Fe14B析出,非晶母相中形成富硼团簇,根据合金成分不同,导致晶化过程中析出不同的相,Nd9Fe78.5Nb0.5B12成分的母合金中先析出的a-Fe晶粒不再生长,而是出现Oswald熟化现象机制,即小的纳米晶a-Fe被大晶粒“吃掉”。硼含量高的母合金Nd9Fe75.5Nb0.5B15晶化过程有Fe23B6和Nd2Fe23B3亚稳相析出。晶化温度升高Nd2Fe23B3分解为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/ 伪 -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/ 伪 -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/ 伪 -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 伪 -Fe precipitated from the master alloy. (II) the TbCu7 metastable phase was decomposed into 伪 -Fe and Nd2Fe14B phases. (2) the crystallization mechanism of 伪 -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，
本文编号：2185323
[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/ 伪 -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/ 伪 -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/ 伪 -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 伪 -Fe precipitated from the master alloy. (II) the TbCu7 metastable phase was decomposed into 伪 -Fe and Nd2Fe14B phases. (2) the crystallization mechanism of 伪 -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，
本文编号：2185323
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