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 Nd2Fe14C phase-based ingot permanent magnets were made by annealing the master alloys. The X-ray diffraction analyses showed that the microstructure consists of Nd2Fe17, Nd2Fe14C and α-Fe phases. Metallography studies showed that after annealing at 950°C for 1h the dispersed inclusions appeared in the center of the main magnetic phase grains. Minor addition of Cu to the Nd20Fe70C9.5B0.5 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 880kA/m for Cu-free and 2at% Cu magnets, respectively. In order to understand the role of Cu atoms during the nucleation and grain growth stage further investigations are required.
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