Crystallization behavior of melt-spun Nd7Fe86Nb1B6 ribbons under different heating rates

The amorphous Nd7Fe86Nb1B6 ribbons were prepared using the melt-spinning method. The relationship between the heating rate up to the annealing temperature and the crystallization behavior was investigated by the calorimetric technique and thermomagnetic measurement. The results show that under the slow heating rate of 10 degrees C/min up to the annealing temperature, the intermediate metastable phases Nd2Fe23B3 and Nd3Fe62B14 are present in the initial crystallization stage. With the increase of temperature, the two phases decompose into the final mixture of Nd2Fe14B and alpha-Fe phases at different temperatures. For the increased heating rate of 30 degrees C/min, all transformations occur at higher temperatures. When the heating rate is further raised to 60 degrees C/min, the intermediate phases Nd2Fe23B3 and Nd3Fe62B14 decompose at the same temperature. When the heating rate is as rapid as 90 degrees C/min, the appearance of intermediate phases was not observed. The result of VSM (vibrating sample magnetometer) measurement shows that magnetic properties can be improved by the increase of heating rate up to the crystallization temperature. The relationship between the heating rate and the microstructure was also studied, (C) 2000 Published by Elsevier Science B.V. All rights reserved.