Structural evolution and improvement of magnetic properties of hot-deformed CeFeB magnets with Nd70Cu30 addition

The low magnetic properties of Ce-based magnets limit their application. In this paper, we aim to improve the coercivity, remanence and maximum energy product of hot-deformed CeFeB magnets by adding low melting Nd70Cu30 alloy. It is found that the addition of Nd70Cu30 remarkably improve the thermal stability and magnetic properties of Ce–Fe–B-based hot-deformed magnets. It is shown by analyzing the microstructure that the proportion of the coarse grain region decreases and the proportion of the liquid region increases in the magnet after adding Nd70Cu30 alloy. The former reduces the nucleation sites of magnetization reversal and the latter weakens the intergranular exchange coupling. Furthermore, the typical core-shell structure was found to be formed in magnets. TEM observation demonstrated that Nd, Ce and Cu were enriched at grain boundaries. Two Curie temperatures were obtained due to different types of 2:14:1 phase, i.e. the incipient CeFeB phase and the newly formed (Nd, Ce)2Fe14B hard magnetic phase. Because of the combined effect of (Nd, Ce)2Fe14B phase and intercrystalline phase, the comprehensive magnetic properties of hot-deformed Ce–Fe–B-based magnets with Nd70Cu30 addition are greatly improved.