Net Shape Processing of Alnico Magnets by Additive Manufacturing

Alternatives to rare earth permanent magnets, such as alnico, will reduce supply instability, increase sustainability, and could decrease the cost of permanent magnets, especially for high-temperature applications, such as traction drive motors. Alnico magnets with moderate coercivity, high remanence, and relatively high-energy product are conventionally processed by directional solidification and (significant) final machining, contributing to increased costs and additional material waste. Additive manufacturing (AM) is developing as a cost effective method to build net-shape 3-D parts with minimal final machining and properties comparable to wrought parts. This paper describes initial studies of net-shape fabrication of alnico magnets by AM using a laser engineered net shaping (LENS) system. High-pressure gas atomized pre-alloyed powders of two different modified alnico "8" compositions, with high purity and sphericity, were built into cylinders using the LENS process, and followed by heat treatment. The magnetic properties showed improvement over their cast and sintered counterparts. The resulting alnico permanent magnets were characterized using scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, and hysteresisgraph measurements. These results display the potential for net-shape processing of alnico permanent magnets for use in next generation traction-drive motors and other applications requiring high temperatures and/or complex engineered part geometries.