A STUDY OF AMORPHOUS FE79B21 ALLOY POWDERS PRODUCED BY CHEMICAL-REDUCTION

Ultrafine amorphous Fe79B21 alloy powders have been successfully produced by chemical reduction. These powders consist of particles of nearly spherical shape with diameters between 100 and 500 nm. A comparison between as-prepared amorphous Fe79B21 powders and Fe80B20 ribbons prepared by melt-spinning is presented. The crystallization behaviour of the Fe79B21 amorphous alloy powders has also been investigated by Mössbauer spectroscopy. A different crystallization behaviour compared with that of amorphous Fe80B20 ribbons has been observed. In the case of Fe80B20 amorphous alloy ribbons produced by the melt-spinning technique, eutectic crystallization is commonly observed resulting in two crystalline phases: α-Fe and Fe3B. This kind of crystallization was not observed in the chemically prepared samples. After annealing, the amorphous powder samples entirely crystallized into three crystalline phases: α-Fe, Fe3B, and Fe2B. The metastable tetragonal Fe3B phase transformed completely into α-Fe and Fe2B after annealing at 973 K for 1 h. © 1990.