Behavior of Nb Atoms in Nb Substituted Nd_(2)Fe_(14)B Nanocrystalline Alloys Investigated by Atom Probe Tomography

摘要

The behavior of Nb atoms in Nd_(12)Fe_(82-x)B_(6)Nb_(x) (x=0 to 3) nanocrystalline alloys has been investigated by using atom probe tomography (APT) technique on near-atomic scale in the present paper. Three-dimensional atom probe (3DAP) analyses on the Nb substituted alloys clearly reveal that Nb atoms are enriched at grain boundaries with a peak concentration about 4 times higher than the average for Nd_(2)Fe_(14)B grains. A grain boundary region with a chemical composition near the Nb:Fe:B stoichiometry of 3:3:5 is also measured for the x=3 alloy. The results provide direct evidence of microstructural refinement due to solute drag of Nb atoms during solidification, resulting in Nb enrichment at grain boundaries and possibly the formation of a Nb-rich interfacial phase which give rise to enhanced magnetic properties.