Magnetic properties, phase evolution, and microstructure of directly cast Nd-Fe-Nb-Sn-B bulk magnets

► Magnetic properties of directly cast Nd9.5Fe75.5−xMxB15 (M = Nb and Sn) bulk magnets are studied. ► Nb substitution is helpful in increasing and refining Nd2Fe14B grains. ► Proper Sn substitution well modifies phase constitution. ► Cosubstitution of refractory and low-melting elements improves magnetic properties of NdFeB magnets.