Crystallization behavior of the cobalt based metallic glass Co₆₅Si₁₅B₁₄Fe₄Ni₂

The cobalt based metallic glass Co₆₅Si₁₅ B₁₄Fe₄Ni₂ has good soft magnetic properties. Its crystallization behavior has been investigated by electrical resistivity, DSC, XRD and TEM. At elevated temperatures, the resistivity is observed to drop at 540, 630 and 750 °C. The first two resistivity drops are consistent with crystallization peaks obtained from DSC experiments. The phases formed are found to be α-Co, ε-Co, Co₂Si, Co₃B₂ in the first crystallization event and Co₂B, Co₄B in the second crystallization event. Supported by the isothermal resistivity results, the crystallization process as observed by TEM is: flower-shaped precipitates forming in the amorphous matrix, sequential nucleation and growth, precipitation inside the grains and at grain boundaries. From electrical resistivity measurement, Curie temperature is found to be 220 °C, and the temperature coefficients of resistivity are calculated to be: 1.12×10^-4 K^-1 in the temperature range 30-220 °C and 0.97×10^-4 K^-1 in the range 220-500 °C of metallic glass Co₆₅Si₁₅B₁₄ Fe₄Ni₂.