Microstructure of high coercivity Nd-Fe-Co-Ga-B hot-deformed magnet improved by the Dy diffusion treatment

► We investigate Dy-diffusion-processed Nd-Fe-B hot-deformed magnet by analytical TEM. ► Thin (Nd,Dy)2Fe14B layer are formed on the surface of Nd2Fe14B grains. ► Dy-substitution occurs preferentially at Nd-sites of a-plane in Nd2Fe14B grain. ► Dy-diffusion-treatment improves the coercivity by forming thin (Nd,Dy)2Fe14B layer.