The invention pertains to the technical field of
rare earth magnetically hard material, in particular to a multi-main-phase Nd-Fe-B type permanent
magnet with high
crack resistance and high coercive force and a preparation method thereof.A final
magnet contains multiple differently-sized hard-magnetic main-phase particles having different anisotropic fields HA. Different main-phase particles account for different volume fractions and are differently distributed, wherein Nd denotes a red earth element having the most content based on the
mass percent. According to
mass percent, the
chemical formula of the permanent
magnet is expressed as (Dd, Re) aFe100-a-b-cBbTmc. By respective selection, different types of main-phase materials such as (Nd, Pr)-Fe-B, (PR, La, Ce)-Fe-B, (Dy, Tb, Ho, Gd, Er)-Fe-B in the ratio of 2:14:1 in order to prepare corresponding coarse
magnetic powder, thin
magnetic powder and magnetic nanocrystalline
powder. Power is utilized for absorbing
hydrogen and controlling
oxygen. Liquid-phase
sintering technology on the pressurized condition at low temperature is adopted for preparation. The multi-main-phase Nd-Fe-B type permanent magnet with high
crack resistance and high coercive force and the preparation method thereof have following beneficial effects: a large piece of magnet does not easily have crack;
crack resistance of the magnet is improved; high coercive force and high
magnetic energy product are obtained; and the preparation technology is suitable for scale production in
engineering.