Investigation of Grain Boundary Compositions and Magnetic Properties of Hot-Worked Nd18Tb1Fe66.5Co5Al1.5B8Magnets

Abstract

Magnetic properties which are related to the compositions on the grain boundaries of the NdFeB permanent magnets were studied at di erent hot working temperatures applied to the cast Nd18Tb1Fe66.5Co5Al1.5B8 ingots. Since the addition of Al caused the formation of hard magnetic μ phase between the magnetic NdFeB crystals after the pressing 800 ◦C Hc value increased to the highest value of 8.21 kOe. According to the SEM micrographs and EDS analysis, the increase in pressing temperature, the atomic ratios in the NdFeAl compositions approached to hard magnetic μ phase with the increase in pressing temperature and its exact composition was obtained in the sample hot deformed at 800 ◦C. Although the secondary μ phase with a high melting temperature is detremental to the alignment of c axis of the magnetic NdFeB grains along the pressing direction, we found that the magnetic properties of the magnets improve due to the presence of this hard magnetic phase on the grain boundaries.