Some Aspects of the Crystallization of Finemet- and Nanoperm-Like Alloys

Abstract

Nanocrystallization in FINEMET- and NANOPERM-like alloys has been studied by less commonly used methods, as resistivity, EXAFS and magneto-elastic measurements. The results are compared with those of classical methods. The less conventional methods show a non-linear relationship of the measured parameter with the transformed fraction. Also evolved heat, as recorded in DSC experiments, is shown to display a similar non-linear relationship in primary crystallization. A common feature of the kinetics of nanocrystallization in all studied compounds is the large tails obtained in the isothermal and non-isothermal treatments, currently described by an Avrami index that changes during the crystallization. In an alternative model, justified by very basic assumptions that should apply to all primary crystallization processes, the observed kinetics is attributed to the change of the activation energy during the transformation.