Brazing and magnetic properties control of sintered NdFeB permanent magnet with high coercivity

This article presents an application of vacuum brazing to join sintered NdFeB permanent magnet N33UH with high coercivity. The magnets were effectively brazed with BCu91AgP Cu-based brazing filler metal at 680°C. The shear strength of the joint was up to 113.19 MPa. Meanwhile, the principal magnetic properties decreased. Subsequently heat treatment for 3 hours at 460-550°C could notably improve magnetic properties. This increase in magnetic properties was mainly attributed to the formation of continuous thin Nd-rich grain boundary phases between the main phases. Heat treated at 520°C, Br, HcB, HcJ, and (BH)max reached 95.4%, 95.9%, 99.8% and 91.4% of as-received magnet, respectively.