Crystallization kinetics and induced magnetic properties of bulk (Fe,Co)-Zr-Nd-B metallic glass

Crystallization kinetics and phase transformation of bulk Fe64Co7Zr6Nd3B70 metallic glass were studied by X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Based on the Kissinger analyses, the activation energies for the nucleation and growth during the first, second and third crystallization-stages of the metallic glass are determined to be 294, 475 and 365 kJ/mol, respectively, and the activation energy for the glass transition is determined to be 1242 kJ/mol. The Johnson-Mehl-Avrami (JMA) analysis under the isothermal condition reveals that the crystallization process is a three-dimensional controlled growth of nuclei at a constant nucleation rate. The crystalline grains are in the size of less than 50 nm after the selected annealing treatments. In the completely crystallized state, the alloy exhibits the maximum coercivity (Hc) of 34.8 kA/m and corresponding energy product of 11 kJ/m3.