Effect of Er30Cu70 on microstructure and properties of sintered Nd-Fe-B by grain boundary reconstruction

Abstract

Usually it is generally believed that the Er element forms the Er2Fe14B phase, which will seriously deteriorate the magnetic properties. Distinctly, here we report the balance of corrosion resistance and coercivity in Nd-Fe-B sintered magnets through using simple Er30Cu70 additive whose price is much lower than Dy and Tb. By reasonably controlling Er30Cu70 addition, the corrosion resistance is improved at the minimum limit of reducing the magnetic properties. Through studying the influence mechanism of Er element, it is found that the main effect of Er elements is to replace the Nd elements at the edge of the main phase grains to form a (Er, Nd)2Fe14B shell with low HA, resulting in the reduction of magnetic properties. The improvement of corrosion resistance mainly comes from the more stable Cu element introduced at the grain boundary. At the same time, the target magnets also show different advantages under different heat treatment methods. Above findings may spur progress towards developing the low-cost permanent magnets that rival the commercial Nd-Fe-B counterpart.