Enhancement of coercivity in sintered Nd-Fe-B magnets by grain-boundary diffusion of electrodeposited Cu-Nd Alloys

• Published in: Metals and materials international Vol. 22; no. 2; pp. 340 - 344
• Main Authors: Lee, Sangjun, Kwon, Jeehye, Cha, Hee-Ryoung, Kim, Kyung Min, Kwon, Hae-Woong, Lee, Junggoo, Lee, Dongyun
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Institute of Metals and Materials 01-03-2016; Springer Nature B.V; 대한금속·재료학회
• Subjects: Antiferromagnetism; BOUNDARIES; Characterization and Evaluation of Materials; Chemistry and Materials Science; Coercive force; Coercivity; Copper; DEPOSITION; Diffraction patterns; DIFFUSION; ELECTRODEPOSITION; ELECTRODES; Electrolytes; Engineering Thermodynamics; Ferrous alloys; Grain boundaries; Grain boundary diffusion; Heat and Mass Transfer; Heat treatment; IRON ALLOYS (50 TO 99 FE); Machines; Magnetic Materials; Magnetism; MAGNETS; Manufacturing; Materials Science; Metallic Materials; Neodymium base alloys; Nitrates; Processes; Scanning electron microscopy; SINTERING; Solid Mechanics; Temperature; 재료공학; plating; diffusion; scanning electron microscopy (SEM); magnetic materials; Coercivity
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-016-5460-8

We report an enhancement in the coercivity of sintered Dy free Nd-Fe-B magnets from 11.84 to 14.26 kOe by the grain-boundary diffusion of electrochemically deposited Cu-Nd. In the optimized electrochemical deposition and heat treatment conditions, a distinct Nd-rich grain-boundary phase was observed after the diffusion process; distributions of each element was carefully mapped by scanning electron microscopy equipped with backscattered electron detector. X-ray diffraction patterns indicated that Nd
2
Fe
14
B was oxidized by the inward diffusion of oxygen, which might be formed during the electrodeposition of Cu-Nd, forming antiferromagnetic Fe
2
O
3
that might degrade the overall coercivity. A mechanism underlying the enhancement of coercivity is basically the same as the well-known proposed mechanism, distribution of a thin Nd-rich phase by grain-boundary diffusion process. In this study, electrochemical deposition process has been extensively investigated, and then the process was demonstrated to be successful and economically useful method to improve coercivity of the magnet.