Effects of alignment on the magnetic and mechanical properties of sintered Nd–Fe–B magnets

Sintered Nd–Fe–B magnets with various degrees of grain alignment are prepared by the conventional powder metallurgy technique. The magnetic properties, bending strength and fracture morphologies of sintered magnets with different alignment degrees are investigated. The results show that the remanence Br and maximum energy product (BH)max increase, while intrinsic coercivity Hcj decreases gradually with increasing the alignment degree. Moreover, the bending strengths measured by applying force parallel (σbb∥) and perpendicular (σbb⊥) to the alignment magnetic field Happl present opposite variation tendency, and σbb∥ is larger than σbb⊥, suggesting the more significant anisotropy of mechanical properties with increasing the degree of grain alignment. Furthermore, the related mechanisms are systematically analyzed.

► The degree of alignment is gradually improved with increasing Happl. ► Br and (BH)max increase, but Hcj decreases with increasing alignment. ► σbb∥ and σbb⊥ present opposite variation law with increasing Happl. ► Fracture morphologies are observed and fracture mechanism is inferred. ► The change mechanisms of properties are systematically analyzed.