CRYSTALLIZATION OF A FINEMET-TYPE ALLOY - NANOCRYSTALLIZATION KINETICS

Crystallization of an Fe74CuNb3Si16B6 alloy was studied by calorimetri c (DSC) and thermomagnetic (TMG) measurements. The first crystallizati on stage produces Fe(Si) nanocrystals, with a mean size of about 10 nm , stable against thermal annealing in an extended temperature/time ran ge. The second stage corresponds to full transformation of the amorpho us matrix and recrystallization of the Fe(Si) nanophase. Nanocrystalli zation kinetics was derived from non-isothermal DSC and from isotherma l TMG data and a good agreement of values for kinetic parameters obtai ned from both analyses was found. The small value, n=1.3, of the Avram i exponent should be related to some special features of the involved mechanisms, such as the increase of quenched-in nucleation sites and t he crystal growth inhibition, during the nanophase formation.