Coercivity enhancement of Nd-Fe-B hot-deformed magnets by the eutectic grain boundary diffusion process using Nd-Ga-Cu and Nd-Fe-Ga-Cu alloys

Nd80Ga15Cu5 and Nd62Fe14Ga20Cu4 alloys were used as diffusion sources for the eutectic grain boundary diffusion process, applying to 4 mm-thick Nd-Fe-B hot-deformed magnets. Both samples showed nearly same coercivity of 2.2 T, while the sample processed with Nd62Fe14Ga20Cu4 showed smaller remanence deterioration from 1.50 T to 1.30 T, in contrast to that of the sample processed with Nd80Ga15Cu5 to 1.08 T. Mr/Ms of the initial sample and the samples processed with Nd62Fe14Ga20Cu4 and Nd80Ga15Cu5 were 0.946, 0.934 and 0.917, respectively, suggesting that the sample processed with Nd62Fe14Ga20Cu4 retains stronger c-axis texture after the diffusion process. Nd-rich phases with Ia3¯ and fcc structures were observed in the sample processed with Nd80Ga15Cu5, while the Nd-rich phases with the Ia3¯ and hcp structures were found in the sample processed with Nd62Fe14Ga20Cu4, all of which are the phases commonly observed in Nd-Fe-B sintered magnets.