Effect of In doping on the evolution of microstructure, magnetic properties and corrosion resistance of NdFeB magnets

The grain boundary phase affects the magnetic properties and corrosion resistance of sintered NdFeB magnets. In this work, a small amount of In was added to NdFeB magnets by induction melting to systematically investigate its effect on the evolution of the microstructure, magnetic properties and corrosion resistance of NdFeB magnets. Microstructural analysis illustrated that minor In addition generated more grain boundary phases and an abundant amorphous phase at the triple-junction grain boundary. While the addition of In failed to enhance the magnetic isolation effect between adjacent matrix grains, its incorporation fortuitously elevated the electrochemical potential of the In-containing magnets. Besides, during corrosion, an In-rich precipitate phase formed, hindering the ingress of the corrosive medium into the magnet. Consequently, this significantly bolstered the corrosion resistance of the sintered NdFeB magnets. The phase formation, magnetic properties and corrosion resistance of In-doped NdFeB magnets are detailed in this work, which provides new prospects for the preparation of high-performance sintered NdFeB magnets.