Changes of microstructure and magnetic properties of Nd-Fe-B sintered magnets by doping Al-Cu

► Cu/Al effects on Nd-Fe-B structure depend on their distribution/alloying behaviors. ► Cu exclusively distributes in grain boundaries different from Al and has negative mixing heat with Nd. ► (Pr,Nd)Cu phase besides CuAl2 forms in grain boundaries with Cu content increase. ► (Pr,Nd)Cu phases optimize microstructure and increase magnetic properties.