Crystallization of Fe-based amorphous alloys

An Fe73.5Si15.5B7Nb3Cu1 alloy with a crystalline grain structure is a soft magnetic material since it has good values of permeability while maintainin g a saturation magnetization. Thermal annealing of an amorphous melt spun a lloy in the temperature range 480-510 degrees C produces a crystalline disp ersion of Fe(Si) particles with diameter of the order of 14 nm embedded in a residual amorphous matrix with a higher crystallization temperature. In t his work we correlate experimental measurements of grain size and crystalli zed fraction of an annealed amorphous Fe73.5Si15.5B7Nb3 Cu-1 ahoy, obtained , respectively, by X-ray diffraction and differential scanning calorimetry, with the particle size observed by transmission electron microscopy. The s tructural development is explained by considering the rejection of insolubl e alloy atoms during crystallization with the formation of diffusion layers around the crystals. Growth rates are diminished by the accumulation of th e slower diffusing atoms at the growing Fe(Si) interfaces; faster diffusing atoms by alloy enrichment of the residual amorphous matrix can cause a dec rease in the nucleation frequency. (C) 1999 Elsevier Science B.V. All right s reserved.