The mechanism of coercivity enhancement by the grain boundary diffusion process of Nd–Fe–B sintered magnets

Coercivity enhancement of hydrogenation–disproportionation–desorption–recombination processed Nd–Fe–B powders by the diffusion of Nd–Cu eutectic alloys

A review is given on the basic properties of 2:14:1 hard magnetic phases as well as technological procedures used for manufacturing R-Fe-B and R-Fe-C permanent magnets. First, we analyse the phase diagrams, crystal structure of hard magnetic phases and composition ranges in which these phases form solid solutions, as a result of various types of substitution. Then, the magnetic properties of and -based compounds are described. The routes used for manufacturing R-Fe-B and R-Fe-C permanent magnets are detailed. The magnets' microstructure as well as their coercivities are described in correlation with composition and manufacturing routes. The properties of nanostructure magnets are then presented. Finally, the stability of Nd-Fe-B and Nd-Fe-C magnets in various working conditions is analysed.

Permanent magnets based on R-Fe-B and R-Fe-C alloys

Microstructure of fine-grained Nd–Fe–B sintered magnets with high coercivity

Distribution of Dy in high-coercivity (Nd,Dy)–Fe–B sintered magnet

The reaction of Dy2O3 or Tb4O7 with Nd15Fe77B8 powder during the sintering increases the coercivity of the sintered magnets. These oxides are reduced to metal during the sintering process, resulting in magnets with properties similar to those prepared from the Nd13.5Dy1.5Fe77B8 alloy.

M. H. Ghandehari

Papers

Reactivity of Dy2O3 and Tb4O7 with Nd15Fe77B8 powder and the coercivity of the sintered magnets