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. M_r/M_s 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.