Effects of Al Nanopowder Intergranular Addition on the Magnetic Properties and Temperature Stability of Sintered Nd-Fe-B Magnet

The effect of Al nanopowders on coercivity and temperature stability of Nd-Fe-B sintered magnets was investigated. With Al nanopowder addition, microstructure modification, magnetic properties, and temperature stability enhancement were investigated in the Nd-Fe-B sintered magnets. The experimental results reveal that the coercivity (Hcj) of the Nd-Fe-B sintered magnet is obviously increased to 1311.8 from 1140.7 kA/m by adding 0.6 wt% Al nanopowders. Meanwhile, the reversible temperature coefficients of coercivity (β) for the sintered Nd-Fe-B magnets are improved from − 0.596 to − 0.572%/°C at 20–140 °C. Furthermore, the irreversible flux magnetic loss (hirr) of the sintered Nd-Fe-B magnets is obviously reduced with the addition of Al nanopowders. Further analysis of the microstructure indicates that a regulated microstructure, i.e., continuous and uniform RE-rich grain boundary (GB) layers, is achieved in the sintered Nd-Fe-B magnets by doping Al nanopowders. In addition, the average grain size decreases to 3.5 from 4.3 μm by adding 0.6 wt% Al nanopowders. It indicates that the introduction of Al nanopowders is promising for preparing excellent-performance Nd-Fe-B sintered magnets with non-rare earth (RE) depletion.