PHASE-TRANSFORMATION AND MAGNETIC-PROPERTIES OF NANOCRYSTALLINE FE73.5CU1NB3SI22.5-XBX (X=6,9) ALLOYS

The coercivity and phase transformations of Fe73.5Cu1Nb3Si22.5-xBx nan ocrystalline alloys as a function of temperature (540 and 620-degrees- C), annealing times (up to 240 min) and compostition (x = 6 and 9) hav e been investigated by means of magnetic measurements, Mossbauer spect roscopy and X-ray diffractometry. Nanocrystalline microstructure after annealing at 540-degrees-C gives rise to a softening of the material, while after annealing at 620-degrees-C for short times a magnetic har dening is observed before a significant increase in size of the alpha- Fe(Sl) grains and the detection of a secondary Fe2B phase. The initial stages of Fe2B precipitation seem to be responsible for this magnetic hardening.