NANOCRYSTALLIZATION IN FE73.5CU1NB3(SI,B)(22.5) ALLOYS - INFLUENCE OFTHE SI B CONTENT/

The influence of Si/B content and annealing conditions on the microstr ucture and magnetic properties of melt-spun FeSiB-CuNb alloys were inv estigated. Heating at temperatures between 750 and 800 K leads to the formation of a nanocrystalline Fe(Si) phase in the amorphous matrix. N anostructure is stable in an extended annealing temperature/time range ; by increasing the annealing temperature only an enhancement of the v olume fraction of the nanophase and a slight increase of the mean grai n size of the nanocrystals are found. Kinetic analysis of the nanocrys tallization reaction gives an anomalously small value of the Avrami ex ponent and it should be related to some special features of the nuclea tion and growth mechanisms in FINEMET-type allows. Heating at temperat ures between 900 and 950 K produces full transformation of the amorpho us matrix. Transition temperatures mean grain size of the nanocrystals and their silicon content, estimated from the Curie temperature, show composition dependence.