Prakt. Met. Sonderband 47 (2015) 107 
hohen™ MICROSTRUCTURAL INVESTIGATION OF CENTRIFUGAL] 
gitar 4 ATOMIZED NdFeB FLAKES USED FOR PRODUCTION OF, 
wh PERMANENT MAGNETS 
M. Bruncko', D. Sojer?, P. Kirbis', I. Anzel] 
Meisämen, / University of Maribor, Faculty of Mechanical Engineering, Slovenia] 
er fir 2 Magneti Ljubljana d.d., Stegne 37, SI-1000 Ljubljana, Slovenia J 
erziehen 
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Whi ABSTRACT] 
Nd—Fe—B-type permanent magnets are widely used in applications that require a high energy 
product/volume ratio in order to reduce weight. Automotive industry, hard drives, or wind turbines; 
are just examples of an application where their use can be found. Conventional casting techniques 
reveal the formation of a high quantity of a-Fe and large Nd-rich regions. On the other hand, new: 
techniques, like strip casting, melt-spinning and centrifugal atomization, produce homogeneous and] 
fine scaled microstructures. od 
‚This paper discusses the application of rapid solidification by the centrifugal atomization method 
for preparation of thin NdFeB flakes. Metallographic characterization is an important way to | 
evaluate material properties, therefore the effect of alloy composition and different conditions of | 
centrifugal atomization on the microstructure of rapidly solidified NdFeB alloy were investigated. 
The microstructures and different phases were examined by optical and scanning electron 
microscopy. Additionally the influence of the processing methods on microstructures of flakes willl 
be discussed. dd 
1. INTRODUCTION 
und thermo-} The rapid solidification technique with high cooling rates allow preparation of alloys with vey 
ewertet. Zi microstructures which are very different from those obtained by conventional casting techniques. In 
und sich Je the case crystalline microstructure, crystals of fine primary phase, supersaturated solid solution and 
rope aid improved chemical homogeneity have been reported [1]. The magnetic properties of the NdFeB 
sch und her magnets are also strongly influenced by morphology its microstructure [2, 3]. Conventional casting] 
iia results in the formation of a high quantity of a-Fe and large Nd-rich regions, while rapid J 
solidification techniques enable higher cooling rates that lead to formation of fine scale ] 
microstructure with higher homogeneity which requires less rare-earth content (Nd+Dy ~ 14 at%) | 
[3-6]. For the centrifugal atomization are also characteristic large cooling rates, which were 1 
achieved by pouring the melt on the rapidly rotating disc. Whereby the melt solidified forming thin 
flakes with thickness about 100 um with fine scale microstructure. ani GG 
[This paper discusses the application of rapid solidification by the centrifugal atomization method § 
for preparation of Nd-Fe-B flakes. The effect of alloy composition and various process parameters 
of centrifugal atomization on the microstructure of rapidly solidified Nd—Fe-B alloy were J 
investigated. The microstructures and the phase composition were examined by metallographic , 
techniques. namely optical and scanning electron microscopy. Additionally the influence of the