Effects of Nb and C additions on the crystallization behavior, microstructure and magnetic properties of B-rich nanocrystalline Nd–Fe–B ribbons

The effects of Nb and C additions on the crystallization behavior, microstructure and magnetic properties of B-rich Nd9.4Fe79.6−xNbxB11−yCy (x = 0, 2, and 4; y = 0, 0.5, and 1.5) alloy ribbons have been investigated. The results show that Nb and C additions change the crystallization behavior of Nd9.4Fe79.6B11, avoid the formation of metastable Nd2Fe23B3 phase, leading to the simultaneously precipitation of α-Fe and Nd2Fe14B phases. The results also show that Nb and C additions suppress the formation and growth of the soft α-Fe phases, leading to the presence of a large amount of Nd2Fe14B phases. Nb and C additions also refine the structure, and thus increase the exchange coupling interaction between the soft and hard phases. Excellent magnetic properties of Br = 0.85 T, iHc = 1106 kA/m, and (BH)max = 117 kJ/m3 have been achieved in Nd9.4Fe75.6Nb4B10.5C0.5 alloy ribbons.