• Kaszuwara, Waldemar
• Michalski, Bartosz

Abstract

<p>The basic phase of the magnetically hard Nd-Fe-B alloys (Nd₂Fe₁₄B) is not stable under the conditions of high-energy milling. When these alloys are milled, the Nd₂Fe₁₄B phase decomposes into Fe and an amorphous phase. A method of improving the structure of this powder is to subject it to annealing at an appropriate temperature which results in the powder acquiring a nanocrystalline structure and excellent magnetic properties. The present paper describes a method of processing the Nd-Fe-B powders in which the milling operation is carried out, entirely or only in the final stage, at high temperatures so that the destruction of the Nd₂Fe₁₄B phase and its recombination occur simultaneously. In this way a powder with good magnetic properties is obtained immediately after milling. In the present experiments the Nd₁₂Fe₈₂B₆ alloy was milled for 17 h at room temperature and, then, the milling was continued for 0.5 h with the powder container heated to an appropriate temperature. The best magnetic properties were achieved in the powder milled at a temperature of about 600°C. Good magnetic properties were also obtained by milling the Nd₁₂Fe₈₂B₆ alloy at a temperature of 600°C maintained during the entire process. They improved with increasing milling time, but even after milling for a long time, the properties of the powder were not as good as those of the powder milled at a high temperature only during the final stage of the process. © 2012 Elsevier B.V. All rights reserved.</p>

Topics

• impedance spectroscopy
• amorphous
• phase
• experiment
• grinding
• milling
• annealing