NANOCRYSTALLIZATION IN FE73.5SI13.5B9CU1NB1X2 (X = NB, MO AND V) ALLOYS STUDIED BY X-RAY SYNCHROTRON-RADIATION

The influence of partial substitution of Nb by refractory elements (Mo and V) on the nanocrystallization process of a FeSiB-CuNb alloy was s tudied by in situ X-ray diffraction, using a synchrotron radiation sou rce. The crystalline volume fraction, the mean grain size of the cryst allites and the nanophase Si content were estimated to describe the mi crostructural al evolution and the kinetics of the process. For the st udied alloys, the volume fraction of the Fe,Si nanophase after anneali ng at the same condition increases in the order Nb < Mo < V. The mean grain size of the Fe,Si nanocrystals also increases in the sequence Nb < Mo < V. Transformation kinetics is described in terms of Johnson-Me hl-Avrami kinetics (JMA) and the obtained values for the overall Avram i exponent are slightly below 1, as usually found for Finemet alloys. (C) 1998 Acta Metallurgica Inc.