Researchers at North Carolina State University have developed a new technique for manufacturing strong magnetic materials. This process improves magnet quality, increases production speed, reduces energy use, and lowers costs.
Strong permanent magnets are important for various technologies, including electric vehicles, wind turbines, and robotic devices. However, current manufacturing methods are complex and energy-intensive. Bharat Gwalani, corresponding author of the study and assistant professor of materials science and engineering at NC State, explained the challenges: “Currently, to manufacture a magnet, industry relies on sintering metal alloy powders into a bulk solid at high temperature and under high pressure. This is a complex, time-consuming process that requires a lot of energy and often results in the creation of flawed magnets.
“For example, the conventional manufacturing process often results in uneven distribution of porosity throughout the magnetic material, with high porosity at the center,” Gwalani said. “This means the magnetic properties of the material are also unevenly distributed.
“One last challenge we wanted to address is related to the fact that the rare earth metals used in producing magnetic materials are very reactive to oxygen,” Gwalani added. “Oxidation adversely affects the magnetic properties of these materials, and high heat increases the rate of oxidation, so we wanted to see if a different process could improve magnet quality.”
The research team tested an alternative approach called friction stir consolidation (FSC). In this method, alloy powder is placed in a chamber under pressure while being stirred with a rotating tool. According to Gwalani: “The energy from the rotational motion and the forge force – the pressure – sinters the powder into a solid without ever melting the alloy. Because the metal is not exposed to high heat and doesn’t actually melt, this process results in less oxidation and unwanted phase transitions in the material. Also, while we are applying pressure, it’s less than one megapascal (MPa), whereas conventional magnet manufacturing techniques apply more than 100 MPa.”
The team found that FSC eliminated porosity within magnets by distributing pressure throughout as it rotates during processing rather than only from top or bottom as with traditional methods. “This is because conventional techniques apply pressure in only one direction, which means the pressure is applied largely to the top and bottom of the material, forcing porosity into the center,” Gwalani said. “Because our technique involves rotating the material as pressure is applied, that pressure is distributed throughout the material.
“In addition, our approach relies on frictional heating caused by alloy powder particles rubbing together,” he continued. “This means heat is being generated at exactly where it’s needed to fuse powders into a bulk solid – there isn’t an external source of heat being applied everywhere as there is in conventional techniques.”
The combination of rotation, frictional heating and lower-pressure application produced magnets free from bubbles or pockets. As Gwalani summarized: “The result is a faster manufacturing method that reduces energy consumption and produces strong permanent magnets with less oxidation and uniform magnetic properties throughout the material.”
Gwalani noted ongoing work aims to further improve magnets by incorporating non-magnetic binder agents for better physical properties such as lower density or reduced reliance on rare-earth elements: “Now that we have figured out a way to consolidate magnetic materials without porosity, we are experimenting with development of next-generation magnets that incorporate non-magnetic binder agents. Our goal is to develop strong permanent magnets that have more desirable physical properties. We want to make low-density tougher magnets that are less reliant on difficult-to-obtain rare-earth materials.”
The research paper appears in Nature Communications under DOI: 10.1038/s41467-025-62804-9.
Co-authors include researchers from North Carolina State University; Pacific Northwest National Laboratory; Stevens Institute of Technology; and Bruker Nano.
Funding was provided by grants from organizations such as Office of Naval Research (grant N00014-23-1-2758), National Science Foundation (grant 2243104), and support from Pacific Northwest National Laboratory through Department of Energy’s Office of Science.
