Microstructure Refinement of Hot Deformed Dy-Free Ndfeb Magnets Through a Novel Cold Sintering Approach by Pressure-Assisted Spark Plasma Sintering
Year: 2025
Type: article
Abstract: Anisotropic fine-grained Dy-free NdFeB high-performance magnets were produced using a novel cold sintering approach by pressure-assisted spark plasma sintering (SPS). The Nd-Fe-B nanocrystalline ribbon powders were subjected to cold sintering below 450°C using pressure-assisted SPS, followed by hot deformation at 710 °C and 810 oC via SPS. Results indicate that cold sintering below 450°C effectively restricts grain growth in the NdFeB magnets, yielding sub-100 nm scale grains across both fine-grained regions and most coarse-grained regions. The refined grain structure achieved through cold sintering allows for a lower hot deformation temperature as compared with the magnet by conventional sintering, as finer grains allow easier deformation and grain sliding/rotation. This process produces a highly fine-grained and anisotropic microstructure to achieve high magnetic performance (i.e., high intrinsic coercivity, remanence, and maximum energy product) in the magnets. Lower hot deformation temperatures help control grain coarsening and limit grain size that is commensurate with the size of a single magnetic domain of the Nd2Fe14B magnetic matrix phase, resulting in high intrinsic coercivity (Hci=11.2 kOe). Furthermore, the reduced hot deformation temperature mitigates the formation of coarse grain bands, leading to improved magnetic properties, specifically an increased remanence (Br = 14.2 kGs) and a high maximum energy product ((BH)max = 47 MGOe).
Source: Journal of Alloys and Compounds
Authors: Ziyi Wu, Dong Zhao, Baozhi Cui, Jie Lian
Institutions: Rensselaer Polytechnic Institute, Ames National Laboratory
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,660
Funder: U.S. Department of Energy
OpenAlex ID: W4414089739