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

The phase transformation and magnetic properties of the NdFe11.35−xVxNb0.65 (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 NdFe11.35−xVxNb0.65 (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 μ0Hc 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)12Nδ. The remanence Jr 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 NdFe11−xNbxV1 (x=0, 0.3, 0.65, 1.0) alloys annealed at 850oC for 20min. 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 μ0Hc of the nitrided alloys monotonically increase, and Jr 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.