Magnetic properties, thermal stabilities and microstructures of melt-spun Misch-Metal-Fe-B alloys

The magnetic properties, thermal stabilities and microstructures of misch-metal (MM) alloys with nominal composition of MM2.0+xFe14B (x = 0-0.6) prepared using melt-spun technique are investigated. The XRD pattern showed that the ribbons consist of the MM2Fe14B main phase, alpha-Fe, Fe3B and ReFe7 phases. The coercivity of all ribbons enhances with increasing the content of MM, while the remanence gradually decreases. Interestingly, there is an increase in remanence of MM2.2Fe14B ribbon, which is attributed to the strong inter-granular exchange coupling effect. The Curie temperature of all the ribbons is around 546 K, which does not change with the content of MM. By the EDS analysis, we have clarified that the changes of the temperature stability are mainly related to the distribution of rare earth content in the main phase. This study shows that the magnetic properties of the alloys can be improved by optimizing the content of rare earth elements. The ribbons in the optimum condition exhibit a coercivity of 899 kA/m and a (BH)(max) of 116 kJ/m(3), which can be used to produce high cost performance MM-Fe-B magnets.