TIME AND TEMPERATURE-DEPENDENCE OF NANOCRYSTALLINE STRUCTURE FORMATION IN A FINEMET-TYPE AMORPHOUS ALLOY

The magnetic softness and nanocrystalline structure formation of Fe73. 5Cu1Nb3Si13.5B9 Finemet alloy as a function of annealing temperature ( 500-600-degrees-C) and annealing time (5 s-3 h) were investigated by m eans of magnetic measurements, DSC and X-ray diffractometry. Annealed at 550-degrees-C the grain size, the solute silicon content of alpha-F e grains and the improvement in magnetic softness saturates as a funct ion of time. The deterioration of the magnetic softness after annealin g at 575-degrees-C is attributed to the Fe3Si compound which segregate s from the alpha-Fe solid solution, giving a third intermediate peak o n the well-known double-peaked DSC diagram. The crystallization produc ts appearing after annealing at 600-degrees-C destroy the intergranula r magnetic coupling and give rise to a magnetic hardening.