Permanent magnets made from rare earth elements are used worldwide in motors and generators associated with wind-based power and electric vehicles, but manufacturing in the U.S. is hampered by several problems. Conventional powder metallurgy processes to create these magnets are both energy- and time-intensive and often waste large amounts of materials during sizing and shaping. These processes also struggle to create permanent magnets with the needed microstructure and bulk density values to ensure robust performance. Pacific Northwest National Laboratory’s friction consolidation fabrication process provides economical manufacturing of permanent magnets and overcomes microstructure and density limitations of conventional metallurgy processes.

The friction consolidation fabrication process focuses on a die tool with a chamber configured to contain process material and one or more plunge tools to compress and/or rotate the material inside the chamber. Simultaneous application of compressive force and rotation-based shear force leads to effective consolidation of powder precursor material, creating a highly refined microstructure with dynamic recrystallization. Because friction consolidation is a solid-state process, the overall temperature of the powder feedstock is always below the melting point, thus a variety of microstructural changes can be made by changing the process variables. As an example, textured and exchanged-coupled nanocomposite permanent magnets based on a mixture of neodymium, iron, and boron could be produced using this method, resulting in magnets that exceed the energy produced by current state-of-the-art magnets. The versatile approach can also extrude forward or backward. Use of active cooling can further help in refining the microstructure in the finished product.

The die tool and plunge tools may be constructed of a variety of alloys, including steel, INCONEL®, aluminum, titanium, nickel, tungsten, and other high-strength alloys. Magnet-forming materials may include neodymium-iron-boron composites, samarium-cobalt composites, iron-silicon composites, and others. Materials may also include combinations of these elements.

Process materials may be in the form of solid ingots, powders with particles or grains of any size, green (i.e., non-sintered) compact powders, amorphous solids, and/or polycrystalline solids.

Applicability

The friction consolidation fabrication process can be used to create a variety of materials, including hard and soft magnetic materials, for use in motors, generators, and other industrial applications.