Mechanical properties and fracture mechanism study of sintered Nd–Fe–B alloy

The mechanical properties including bending strength (σbb) and fracture toughness (KIC) of sintered Nd–Fe–B magnets have been examined in this paper. Alloyed magnet with Dy, Co, Nb additions shows the higher magnetic properties and bending strength but the lower fracture toughness than the ternary magnet. The zero plastic energy in bending procedure presents the purely brittle nature of Nd–Fe–B magnet. Fracture mechanism has been discussed on the base of the in situ SEM observation of micro-crack nucleation and FE-SEM (field emission scanning electron microscope) observation of indentation cracks. The fracture mechanism of sintered Nd–Fe–B alloy is concluded as two stages: the damage-accumulating stage and the crack-propagating stage. Some suggestions for improving toughness of sintered Nd–Fe–B magnets are mentioned.