Non-isothermal crystallization kinetics and hard magnetic properties of Hf1.5Zr0.5Co10FeB melt-spun ribbons

Thermal and kinetic analysis of the partially crystallized Hf1.5Zr0.5Co10FeB melt-spun (MS) ribbon was carried out by differential scanning calorimetry (DSC) through non-isothermal method which conforms to the Johnson-Mehl-Avrami (JMA) model. DSC curves indicate a three-step exothermic crystallization process for the heating rates 5, 7.5, 10 and 15 K min(-1) studied in the present work. The influence of the heating rate for tertiary crystallization event is larger than the primary and secondary crystallization, and the analysis of the tertiary crystallization has been estimated in this study. The kinetics of crystallization gives the values of apparent activation energies of 233.4 +/- 12.4 kJ mol(-1) and 244.8 +/- 12.3 kJ mol(-1) according to Kissinger and Ozawa's model for the decomposition of metastable phases, respectively. The non-isothermal crystallization kinetics was modelled by the JMA equation, and the Avrami exponent was calculated in the range of 4.25-1.51. This implies that the crystallization of Hf1.5Zr0.5Co10FeB alloy is governed by three-dimensional growth at the beginning of the crystallization and transforms to one-dimensional growth at the end. The crystalline phases in the optimized annealed samples were confirmed by X-ray diffraction. The microstructural dependence of grain growth of the MS ribbon upon annealing was investigated by scanning electron microscopy. Magnetic hysteresis loop measurements of MS ribbons revealed the evolution of hard magnetic properties upon annealing at 823 K. This study provides a new insight into tailoring the microstructure and magnetic properties of Hf1.5Zr0.5Co10FeB MS ribbons by optimizing process parameters based on crystallization kinetics.