About this Abstract |
| Meeting |
2027 TMS Annual Meeting & Exhibition
|
| Symposium
|
Advances in Magnetism and Magnetic Materials
|
| Presentation Title |
Optimizing the Grain Size–Coercivity Relationship in Nanograined NdFeB Magnets via Hot-Rolling and Post-Roll Annealing |
| Author(s) |
Chaochao Pan, Jack Page, Micah Vemu, Wei Tang, Jun Cui |
| On-Site Speaker (Planned) |
Chaochao Pan |
| Abstract Scope |
For almost a century, materials scientists have striven to resolve Brown’s paradox, the phenomenon where the experimental coercivity of a permanent magnet is less than 30% of its theoretical limit. Conventional strategies to bridge this gap rely on microstructural optimization involving defect control, grain refinement, and grain boundary modifications. This study investigates the relationship between grain size and coercivity in nanograined NdFeB magnets. In isotropic melt-spun ribbons, coercivity decreases monotonically with increasing grain size. However, in hot-rolled anisotropic bulk magnets, the coercivity peaks at an intermediate grain size. Excessively small grains suffer from strong intergranular exchange coupling, whereas oversized grains facilitate easy reverse domain nucleation and wall propagation. Furthermore, post-roll annealing near the melting point of the Nd-rich phase simultaneously improvs both coercivity and the M-H loop squareness factor by optimizing the grain boundary phase. These findings provide critical microstructural pathways to engineer high-performance, heavy-rare-earth-free NdFeB magnets. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
Magnetic Materials, |