Processing of Alnico Magnets by Additive Manufacturing

Abstract

Permanent magnets without rare earth (RE) elements, such as alnico, will improve supply stability and potentially decrease permanent magnet cost, especially for traction drive motors and other increased temperature applications. Commercial alnico magnets with the highest energy product are produced by directional solidification (DS) to achieve a <001> columnar grain orientation followed by significant final machining, adding to the high cost. Additive manufacturing (AM) is an effective method to process near net-shape parts with minimal final machining of complex geometries. AM also, has potential for texture/grain orientation control and compositionally graded structures. This report describes fabrication of alnico magnets by AM using both laser engineered net shaping (LENS)/directed energy deposition (DED) and electron beam melting powder bed fusion (EBM/PBF). High pressure gas atomized (HPGA) pre-alloyed alnico powders, with high purity and sphericity, were built into cylindrical and rectangular samples, followed by magnetic annealing (MA) and a full heat treatment (FHT). The magnetic properties of these AM processed specimens were different from their cast and sintered counterparts of the same composition and show a great sensitivity to heat treatment. The AM process parameters used in this developmental study did not yet result in any preferred texture within the alnico AM builds. These findings demonstrate feasibility for near net-shape processing of alnico permanent magnets for use in next generation traction drive motors and other applications requiring increased operating temperatures and/or complex engineered part geometries, especially with further AM process development for texture control.

Preparation of Cobalt Nanoparticles

“…Thus, cobalt is used widely as one of the metals needed to create hard permanent magnets with high coercivity, such as the aluminium‐nickel‐cobalt (Al−Ni−Co, “Alnico”) alloy series. Alnico magnets are used in motors, hard disk drives, and sensors [132–135] . Magnetic resonance imaging (MRI) is another example of an application for these magnetic alloys [136,137] .…”

Manufacturing Processes for Permanent Magnets: Part I—Sintering and Casting

“…Additive manufacturing (AM) methods have been explored for alnico manufacturing. 52 The commercial alnico magnets with the highest energy performance are produced by directional solidification followed by significant machining. These magnets achieve perfect columnar grain orientation but are costly.…”

“…Both laser engineered net shaping and electron beam melting powder bed fusion methods were tested for alnico additive manufacturing. 52,53 Figure 13 shows the parts made with these two methods. The properties of the AM processed samples are less than ideal.…”

Additive Manufacturing of Pure Mo and Mo + TiC MMC Alloy by Electron Beam Powder Bed Fusion

“…Details of the system capabilities are described elsewhere. [19][20][21] Six cylindrical specimens measuring 12 mm in diameter by 13 mm tall were fabricated with software version 3.2 SP2. The composition of the samples was varied in three distinct regions as illustrated in Fig.…”