Effect of stress on crystallization behavior in a Fe-based amorphous ribbon: An in situ synchrotron radiation X-ray diffraction study

The microstructure evolution of FeCuNbSiB amorphous alloys during stress nanocrystallization has been investigated by in situ synchrotron XRD and ex situ TEM. It is found that the average grain sizes in the stress-annealed samples (SA) and without stress (FA) are 8.6 nm and 10.9 nm, respectively. The volume fraction of the α-Fe(Si) phase increases from 7% to 64% for the SA sample and from 1% to 62% for the FA sample after the soaking stage of the annealing process. The grain size also decreases with increasing tensile stress for the different stress-annealed samples. These results reveal that the tensile stress during annealing reduces Gibbs free energy which promotes nucleation rate, resulting in significantly smaller crystallite sizes.