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  • Rapid coercivity increment ...
    Liu, Xiaolian; Wang, Xuejiao; Liang, Liping; Zhang, Pei; Jin, Jiaying; Zhang, Yujing; Ma, Tianyu; Yan, Mi

    Journal of magnetism and magnetic materials, 12/2014, Volume: 370
    Journal Article

    To enhance coercivity and reduce the rare-earth consumption of Nd–Fe–B sintered magnets simultaneously, low melting point Dy69Ni31 (at%) powders are introduced into a slightly off-stoichiometric Nd2Fe14B (2:14:1 phase) (Pr, Nd)12.36FebalB6.09 (at%) starting magnet. Because of insufficient rare-earth element, the starting magnet possesses discontinuous intergranular grain boundaries (GBs) that cannot decouple the 2:14:1 phase grains well, hence leading to a low coercivity of only 9.53kOe. The Dy69Ni31 additive provides extra rare-earth that improves the liquid-phase sintering with the formation of continuous intergranular GBs, accompanied by the diffusion of Dy towards surface region of the 2:14:1 phase grains. A significant increment in coercivity of 6.25kOe is realized with a slight reduction in remanence by −3.0% per unit at% Dy. Satisfactory magnetic performance with (BH)max=47.49 MGOe, Br=13.92 kGs and Hcj=13.93kOe, is obtained in the magnet containing only 12.92 at% rare-earth elements, in which 0.68 at% Dy is included. It combines advantages of the modification of intergranular GBs and the formation of a magnetically hardening shell surrounding 2:14:1 phase grains, which can be a promising approach to fabricate low rare-earth and high performance Nd–Fe–B magnets for mass production. •Dy–Ni powders are introduced into slightly off-stoichiometric 2:14:1 type magnets.•Both morphology and composition are restructured in intergranular regions.•Rapid increment of coercivity and slight reduction in remanence are obtained.•Total rare-earth consumption is reduced simultaneously.