Comparison of the Thermomagnetic and Thermal Effects duringNanocrystallization of Amorphous Fe_(76.5-x)Cu_1Nb_xSi_(13.5)B_9 Alloys

The results of thermomagnetic (TM) and calorimetric (DSC) measurements have been compared in order to clarify some details of the mechanism of nanophase-formation from Finemet-type precursors with different Nb contents. It was found that the main features of the DSC thermograms (shape, relative separation and amplitude of the exothermic peaks characteristic for the precipitation of the Fe-(Si) solid solution and the transition metal borides) depend mainly on the composition of the precursor glass, and are only slightly affected by the heating rate between 20 and 80 K/min. The amplitude of the uprise of the magnetization in the TM curves (attributed to the precipitation of bcc-Fe(Si) and borides) decreases with increasing Nb-content. The Curietemperature of the precursor glasses. Tc(am1), the remainder amorphous phases, Tc(am2) and the bcc nanophase, Tc(n-Fe) are determined from the thermomagnetic curves. The shape of the TM curves is interpreted on the basis of the reactions describing the crystalIization of the hypo-eutectic Fe-B glasses.