Nanocrystallization of α-Fe Crystals in Fe52Cr18Mo7B16C4Nb3 Bulk Amorphous Alloy

Crystallization kinetics of Fe52Cr18Mo7B16C4Nb3 alloy was evaluated by X-ray diffraction (XRD), differential scanning calorimetric (DSC) tests and transmission electron microscopy (TEM) observations in this research work. In effect, crystallization and growth mechanism were investigated by using DSC tests at four different heating rates (10, 20, 30, 40 K/min). Results showed that a two-step crystallization process occurred in the alloy in which α-Fe and Fe3B phases were crystallized, respectively in the structure after heat treatment. Activation energy for the first step of crystallization, i.e. α-Fe was measured to be 421 and 442 kJ/mol according to Kissinger-Starink and Ozawa models, respectively. Further, Avrami exponent calculated from DSC curves was 1.6 and a two-dimensional diffusion controlled growth mechanism with decreasing nucleation rate was observed in the alloy. Moreover, it was known from the TEM observations that crystalline α-Fe phase nucleated in the structure of the alloy in an average size of 10 nm and completely mottled morphology.