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.
Highlights
Research into viable alternative magnet solutions is motivated by price fluctuations and supply uncertainty of rare earth oxides and metals (e.g., Dy, Nd, and Pr), which are key components in high energy product (BHmax ) rare earth (RE) permanent magnets [1,2]
Chemistry powder compositions used in this study as determined by inductively coupled plasma-mass spectrometry (ICP-MS) are included in Table 5, 3.1.1.The
Alnico magnets have been successfully produced using Additive manufacturing (AM) processing from pre-alloyed powders of custom compositions using both directed energy deposition (DED) and electron beam melting powder bed fusion (EBM/PBF) methods over a range of processing parameters
Summary
Research into viable alternative magnet solutions is motivated by price fluctuations and supply uncertainty of rare earth oxides and metals (e.g., Dy, Nd, and Pr), which are key components in high energy product (BHmax ) rare earth (RE) permanent magnets [1,2]. Alternative permanent magnets, such as alnico, with significant improvement, provide the prospect of reduced supply instability and. Generation motor designs for automotive applications presently exist that utilize alnico magnets considering projected elevated temperature energy products [1]
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