Crystallisation process in (FeCo)78Nb6(BCu)16 alloys

Crystallisations of Fe78−xCoxNb6B16−yCuy (x=18,39,60; y=0, 1) alloys at different heating rates have been studied by differential scanning calorimetry (DSC), thermomagnetic gravimetry (TMG), and X-ray diffraction techniques. α-Fe,Co nanometer sized crystals dispersed in a residual amorphous matrix are obtained in a first stage and the crystallisation is completed after a second stage with the formation of various boride phases. Co alloying decreases the temperature for the crystallisation onset and increases the Curie temperature of the amorphous phase. The volume fraction and the lattice parameters of the α-Fe,Co crystals decrease as the Co content in the alloy increases. The Avrami exponents for the first crystallisation stage are approximately 1.