Thermomagnetic Behaviour and Microstructure of a Rapidly Quenched $Nd_{4.5}Fe_{77}B_{18.5}$ Alloy

Changes in the phase composition and crystallite size, as well as changes in the magnetic behaviour of $Nd_{4.5}Fe_{77}B_{18.5}$ alloy, caused by thermomagnetic measurements, was observed in regard of the optimal magnetic state of this alloy. In the optimized magnetic state, the formed nanocomposite consisted of $Fe_3B//Nd_2Fe_{14}B$ and partly of α-Fe with a mean crystallite size < 30 nm, as determined by X-ray diffraction and transmission electron microscopy. An increased amount of α-Fe, the presence of $Nd_2O_3$ and different Fe-B phases, as well as an increase in the mean crystallite size were observed after thermomagnetic measurements had caused a quality loss of the hard magnetic properties.