Effect of Ti + C addition on quenchability and magnetic properties of Nd 9 Fe 85 B 6
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Effect of Ti + C addition on quenchability and magnetic properties of Nd9Fe85B6 T.M. Zhao,a) X.R. Xu, and Z.Q. Hu State Key Laboratory for Rapidly Solidified Alloys, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, People’s Republic of China
Ingots of composition Nd9Fe85B6, Nd9Fe85B6 + 1 at.% (Ti + C), Nd9Fe85B6 + 2 at.% (Ti + C), and Nd9Fe85B6 + 5 at.% (Ti + C) were prepared by plasma arc-melting the constituent elements from 99.95 wt% Nd, 99.99 wt% Fe, 99.97 wt% Ti, spectrographic grade C, and ferroalloy Fe–B (19.6 wt% B). Effect of Ti + C addition and its content on quenchability and magnetic properties of Nd9Fe85B6 alloy were investigated by melt-spinning. The results showed that the added Ti and C elements reacted with each other to form TiC compound that was solid solutioned, precipitated, or both in the cast ingots. The Ti + C addition can increase the glass-forming ability (GFA) of an ␣–Fe/Nd2Fe14B–type nanocomposite permanent material: the more the additive, the stronger the GFA; but only approximately 2 at.% Ti + C addition could enormously increase the magnetic properties.
I. INTRODUCTION
II. EXPERIMENTAL PROCEDURES
A new and realistic way to combine a large magnetization of a soft magnetic phase and a high magnetocrystalline anisotropy of a hard magnetic phase is to develop a microstructure in nanoscale in which the two phases mutually couple by intergrain exchange interactions. A typical example among them is an ␣–Fe/Nd2Fe14B system in which a fine nanocrystalline mixture develops from a melt-quenched amorphous material by a subsequent heat treatment. Because of the low glass-forming ability (GFA) of this kind of material, more than 40 m/s wheel speed is needed to obtain the full amorphous state. Optimum wheel speed is usually used in industry to directly get the ␣–Fe/Nd2Fe14B nanocomposite magnet; however, the narrow optimum speed zone makes it difficult for the process to be stably controlled. Ti, C, or Ti + C additions can greatly increase the GFA of Nd2Fe14B, which has potential application in production of atomized Nd–Fe–B powders.1–4 If Ti + C addition can also improve the GFA of an ␣–Fe/ Nd2Fe14B alloy without any influence on its magnetic properties, it will be helpful in industry process. The purposes of this article are to investigate the effects of Ti + C addition together with its content on quenchability and magnetic properties of Nd9Fe85B6 and to briefly discuss these effects.
Ingots of composition Nd9Fe85B6, Nd9Fe85B6 + 1 at.% (Ti + C), Nd9Fe85B6 + 2 at.% (Ti + C), and Nd9Fe85B6 + 5 at.% (Ti + C) were prepared by plasma arc-melting the constituent elements from 99.95 wt% Nd, 99.99 wt% Fe, 99.97 wt% Ti, spectrographic grade C, and ferroalloy Fe–B (19.6 wt% B) in an ultrahigh-purity (UHP) argon atmosphere. Each ingot was flipped and remelted several times to ensure homogeneity. Approximately a 30-g piece of ingot was melt-spun each time with a conventional melt-spinner. A direct current servo motor gave precise con
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