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 studied by in situ X-ray diffraction, using a synchrotron radiation source. The crystalline volume fraction, the mean grain size of the crystallites and the nanophase Si content were estimated to describe the microstructural al evolution and the kinetics of the process. For the studied alloys, the volume fraction of the Fe,Si nanophase after annealing 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-Mehl-Avrami kinetics (JMA) and the obtained values for the overall Avrami exponent are slightly below 1, as usually found for Finemet alloys. (C) 1998 Acta Metallurgica Inc.