PROPERTIES OF SINTERED AL SUBSTITUTED NDFEB MAGNETS

The effect of partial substitution of Fe by Al (Al, Al2O3) on the magn etic properties and the corrosion resistance of the sintered NdFeB mag net has been investigated. With the increasing amount of Al, the aniso tropy field and the saturation magnetization decrease, but the coerciv ity increases up to 4 at.% Al and further alloying of Al leads to a de crease of the coercivity. Different substances like Al (metallic Al or Al2O3) modify the microstructure to different increase in the coerciv ity and especially to changes in the remanence. Alloying Al via metall ic Al decreases the remanence, whereas via Al2O3 up to 4 at.% Al incre ases it. The Al additions inhibit atmospheric corrosion of the magnet. We have found that Al2O3 in sintered NdFeB magnet substantially impro ves the coercivity and the corrosion resistance with the improved rema nence.