Effect of replacement of Ni by Co on thermal stability of Fe40Co40P14B6 metallic glass

Effects of full replacement of Ni by Co in the well-known Fe40Ni40P14B6 glass on thermal stability and structure of fully crystallized samples were investigated by differential scanning calorimetry and transmission electron microscopy. Both glasses crystallize via the same eutectic mode however the crystallization temperatures of the Fe40Co40P14B6 glass are about 60 K higher. Kinetics of eutectic crystallization of amorphous alloys at constant rate heating and structure of crystallized samples have been investigated by differential scanning calorimetry and transmission electron microscopy, respectively. The values of the specific free energy of the crystal/glass interface and the effective interfacial diffusion coefficient, which define the crystal nucleation and growth in these glasses, were extracted from both the kinetic and structural data using the earlier proposed method. The obtained results showed that the enhanced thermal stability of the Fe40Co40P14B6 glass was caused mainly by the essential lowered values of crystal growth rate.