Metastable nanocrystalline A(1) phase and coercivity in Fe-Nd alloys

Transmission electron microscopy observations of as-cast hypoeutectic FexNd 100-x alloys (x > 25) show that meta stable Fe-rich and Nd-rich phases form the eutectic areas in its microstructure. The heat treatment of as-cast al loys at temperatures lower than 600 degrees C does not result in the change of thermomagnetic data and hysteresis properties. Thermomagnetic data and increased H-cJ (up to 80-400 kA/m of hypoeutectic alloys after heat treatme nt at temperatures 600-740 degrees C indicate an increase in the amount of the hard magnetic phase (T-c = 245 degrees C) in its microstructure. High-r esolution electron microscopy investigations of heat-treated alloys indicat e the formation of the nanocrystalline A(x) phase inside the Fe-rich compon ent of the metastable eutectic. The appearance of the A(x) phase, which is the same as the well-known highly anisotropic A(1) phase, increases the coe rcivity of hypoeutectic Fe-Nd alloys after heat-treatment. (C) 1999 Publish ed by Elsevier Science B.V. All rights reserved.