MODELING OF NANOCRYSTALLIZATION IN FINEMET-TYPE ALLOY FROM ENTHALPY MEASUREMENTS

We have studied the enthalpy changes in Fe73.5Cu1Nb3Si13.5B9 alloy alo ng isothermal DSC runs and performed X-ray diffraction (XRD) on anneal ed samples. The average grain size of nanograins presents a limit near ly independent of temperature (approximate to 12 nm). Modelling of the enthalpy variations was performed and good agreement with experiments is observed in the low temperature range. When the temperature is inc reased, steady-state nucleation seems to be invalid for long annealing times. A plausible explanation is presented involving the formation o f a Nh diffusion layer around the nanograins.