ADVANCES IN PROCESSING, MANUFACTURING, AND APPLICATIONS OF MAGNETIC MATERIALS Manufacturing Processes for Permanent Magnets: Part I—Sintering and Casting JUN CUI , 1,2,3,7 JOHN ORMEROD, 1,4 DAVID PARKER, 1,5 RYAN OTT , 1,2 ANDRIY PALASYUK, 1,2 SCOTT MCCALL, 1,6 M. PARANS PARANTHAMAN , 1,5 MICHAEL S. KESLER, 1,5 MICHAEL A. MCGUIRE, 1,5 IKENNA C. NLEBEDIM , 1,2 CHAOCHAO PAN, 1,2,3 and THOMAS LOGRASSO 1,2,3 1.—Critical Materials Institute, Ames, IA 50011, USA. 2.—Ames Laboratory, Ames, IA 50011, USA. 3.—Material Science and Engineering Department, Iowa State University, Ames, IA 50011, USA. 4.—JOC LLC, Loudon, TN 37774, USA. 5.—Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. 6.—Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. 7.—e-mail: cuijun@ameslab.gov Permanent magnets (PMs) produce magnetic fields and maintain the field even in the presence of an opposing magnetic field. Electrical machines using permanent magnets are more efficient than those without. Currently, all known strong magnets contain rare earth (RE) elements, and they are core components of a wide range of applications including electric vehicles and wind turbines. RE elements such as Nd and Dy have become critical materials due to the growing demand and constrained supply. Improving the manu- facturing process is effective in mitigating the RE criticality issue by reducing waste and improving parts consistency. In this article, the state of the industry for PM is reviewed in detail considering both the technical and eco- nomic drivers. The importance of RE elements is discussed along with their economic importance to green energy. The conventional sintering and casting manufacturing processes for commercial magnets, including Nd-Fe-B, Sm-Co, Alnico, and ferrite, are described in detail. INTRODUCTION ‘‘A magnet is fundamentally an energy-storage device. This energy is put into it when it is first magnetized, and it remains in the magnet indefi- nitely, if properly made and properly handled’’. 1 Unlike in a battery, a magnet’s energy is not drained away and always available for use. This is because a magnet does not do a net work on its surroundings; instead, a magnet lends its energy to attract or repel other magnetic objects, thereby assisting in converting between electrical and mechanical energy. A permanent magnet is unique in that once produced, it provides a magnetic flux with no energy input, hence zero operating cost. By contrast, electromagnets require a continuous elec- trical current to generate a magnetic field and operate. Permanent magnets today are used in a wide range of motors, wind turbines, electronics, and medical devices. Their special technological importance derives from the ability to act without contact, by either attraction or repulsion, interact with and generate a force on a charged particle or a conductor carrying an electrical current. Figure 1 shows the major device types using permanent magnets. Key Figures of Merit Magnetization is the sum of the electron spin and orbital moments per unit volume in a material, and in ferromagnets these moments align over long ranges to provide values of magnetization millions of times greater than most materials. The distin- guishing characteristic of a PM is that it can produce and maintain magnetic fields even in the presence of an opposing external magnetic field. But if the opposing field’s magnitude is strong enough, (Received May 27, 2021; accepted January 3, 2022) JOM https://doi.org/10.1007/s11837-022-05156-9 Ó 2022 The Author(s)