Phase transformation and magnetic properties of Nd–Fe–V–Nb alloys prepared by mechanical alloying

Abstract

The phase transformation and magnetic properties of the NdFe 11.35− x V x Nb 0.65 ( x=0–1.35) alloys prepared by mechanical alloying (MA) have been studied. Phases of 2:17, 1:7 and 1:12 are formed in the as-annealed alloys with x=0, 0.3–0.7 and 1.0–1.35, respectively. With increasing V content in the NdFe 11.35− x V x Nb 0.65 ( x=0.3–0.7) alloys, the Curie temperatures of the matrix 1:7 phases monotonically increase. Upon nitrogenation, with increasing V content, the intrinsic coercivity μ 0 H c of the nitrided alloys monotonically increases. The increase becomes sharp at x=1.0 due to the formation of a great amount of Nd(Fe, V) 12N δ . The remanence J r and the maximum magnetic energy product (BH) max of the nitrided alloys monotonically decrease with increasing V content. The 1:12 phases are formed in all the NdFe 11− x Nb x V 1 ( x=0, 0.3, 0.65, 1.0) alloys annealed at 850 oC for 20 min. With increasing Nb content, the crystallization of the 1:12 phase is improved and the relative volume fraction of the 1:12 phase tends to be higher. While μ 0 H c of the nitrided alloys monotonically increase, and J r and (BH) max of the nitrided alloys monotonically decrease. With increasing Nb content in the nitrided alloys, the average grain size of α-Fe decrease while the nitrogen content increases.