Magnetic properties and microstructure of Nd–Fe–B–C magnets with Cu addition

Abstract The effect of Cu addition and annealing treatment on the microstructure and hard magnetic properties of Nd–Fe–C–B ingot-type permanent magnets was investigated. The Nd 2 Fe 14 C phase-based ingot permanent magnets were made by annealing the master alloys. The X-ray diffraction analyses showed that the microstructure consists of Nd 2 Fe 17 , Nd 2 Fe 14 C and α -Fe phases. Metallography studies showed that after annealing at 950 °C for 1 h the dispersed inclusions appeared in the center of the main magnetic phase grains. Minor addition of Cu to the Nd 20 Fe 70 C 9.5 B 0.5 cast alloy is effective in enhancing the coercivity of ingot Nd–Fe–C–B-type permanent magnets. The coercivities for magnets annealed at 950 °C are 630 and 880 kA/m for Cu-free and 2 at% Cu magnets, respectively. In order to understand the role of Cu atoms during the nucleation and grain growth stage further investigations are required.