Additive Manufacturing of Permanent Magnetic NdFeB Using Laser Powder Bed Fusion—Process-Structure-Property Relationships

The interest in additive manufacturing (AM) of functional materials is growing at a significantly fast pace. The use of metal AM processes with magnetic materials to fabricate devices rather than components has seen a lot of development over the past years. The permanent magnetic material NdFeB combined with the plethora of advantages that AM has to offer promises new prospects in various application sectors, such as electric motors. However, being a brittle material, NdFeB poses a lot of challenges when processed by a technique such as laser powder bed fusion (L-PBF). In this work, we present a comprehensive understanding of the cracking phenomenon that occurs during producing these magnets and propose means of mitigation. The microstructural features, their formation mechanisms and phase transformations during the characteristic layer-by-layer processing in L-PBF, were investigated. The structural integrity of the printed magnets was also evaluated. Although the parametric study enabled reducing the crack content in the fabricated structures, residual cracking remained that compromised the mechanical performance of the magnets. Therefore, infiltration was proven successful to improve the structural integrity of the manufactured magnets. Most importantly, the magnetic properties were measured and correlated to the process parameters and the metallurgy of the manufactured parts. Nevertheless, the influence of post-process heat treatments on the microstructure and magnetic properties were studied. Lastly, a demonstration for using the printed magnets in a motor is presented.