C. Pan, W. Tang, X. Liu, I. Nlebedim, O. Ryan, J. Cui
Ames National Laboratory,
United States
Keywords: anisotropic NdFeB, Dy-free, hot-roll, continuous production, near-net-shape production
Summary:
Nd-Fe-B is the most powerful magnet at room temperature. It plays a dominant role in energy efficiency and renewable energy applications due to its high energy density. However, making Nd-Fe-B magnets, especially into small sizes or odd shape with high aspect ratio, can be challenging and costly because of machining failure and low productivity of the conventional batch processing. Moreover, Nd-Fe-B needs critical heavy rare earth elements to be functional at elevated temperature. One approach to bypass this HRE criticality issue is to utilize the grain size effect on coercivity, e.g., nanograin size magnet can perform the same as the micron-grain size magnet with 4-6% of Dy. However, making nanograin magnet requires a two-step process: hot-press for densification and hot-deformation for texture development. It is an inherently expensive process. Here, we report a novel Nd-Fe-B fabrication method that is continuous and near-net-shape. The process starts with loading Nd-Fe-B powders into a metal container, packing the powder to 60% dense, then hot-rolling the powders into full density. We showed that hot rolling at ~790 °C with 70% thickness reduction can result in nearly full density anisotropic magnet with high energy product (40 MGOe). This novel method allows cost-effective production of near-net-shape Nd-Fe-B magnetic with good and consistent magnetic properties.