With the addition of Al and/or Cu into the NdFeB based magnet, the soft free iron phase was not observed in the cast alloys while it exists in the microstructure of the undoped NdFeB ingots. For the undoped sample, free iron disappeared after hot deformation process. Grain orientation is not good and there are deviations in the growth direction of the lamellar grains which are not perpendicular to the pressing direction. On the other hand, there is a striking change that the intergranular chemistry of Al added ingot separated into Nd-rich phase and a ternary FeNdAl composition most probably formed at the pressing temperature of 750• C. The highest remanent magnetization of 7.47 kG obtained for this sample, it might be due to the hard magnetic properties of this ternary composition. For the AlCu added sample, the high Hc and Br values of 7.71 kOe and 7.33 kG, respectively, can be attributed to the homogeneous distribution of the intergranular composition and good orientation of the magnetic grains by hot deformation process.

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With the boron addition, the Curie temperature of Sm2Fe17 permanent magnet was observed to increase from 130 • C and reach its highest value of 362 • C for the sample at x = 4. In the X-ray diffraction measurements, the peaks diffracted from the planes of hard magnetic Sm2Fe17 phase, observed in the sample without boron, disappeared with the boron addition and magnetic SmFe3 and Fe2B phases were detected. For all samples, the major peaks belong to the α-Fe phase. According to the magnetization measurements, the Ms value of the sample without boron is 155.52 emu/g, it decreased to its lowest value of 97.93 emu/g for the sample at x = 4. Boron addition resulted in an evolution of the phase constitution that caused changes in magnetic properties of the alloys.

Magnetic properties which are related to the compositions on the grain boundaries of the NdFeB permanent magnets were studied at dierent 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.

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