Additive Manufacturing of Amorphous Soft Magnetic Materials

Abstract

Amorphous alloys intended for soft-magnetic applications are commonly produced through the rapid solidification of the molten metal. Typically, these alloys are prepared by incorporating metalloids (such as Si, B, Al, C, and P) into Fe-based and Co-based alloys, constituting approximately 20% of the composition. In amorphous magnetic alloys, the microstructure is characterized by the absence of atomic long-range order, showcasing only short-range order. This short-range order stems from the essentially random atomic arrangement during the solidification of the liquid melt at a cooling rate ranging from 105 to 106 K/s. Consequently, the absence of crystallite-related defects, such as grain boundaries and dislocations, contributes to a reduction in coercivity. Numerous studies have explored Fe-and Co-based magnetic materials produced through additive manufacturing (AM), given their broad applicability in the energy sector. While certain soft-magnetic amorphous/nanocrystalline alloys, such as the commercially available FeSiBCuNb alloys (FINEMET), show excellent soft-magnetic properties, AM has not yet introduced commercially available amorphous or nanocrystalline alloys. These materials are still at the research stage. Notably, the significant challenges lie in substantial crystallization and the segregation of alloying elements in AM, particularly when dealing with conventional alloying systems that exhibit low glass-forming ability (GFA). An innovative scanning strategy enabled the successful achievement of nearly 90% amorphous content in the laser additive manufactured FeSiBCrC alloy, which initially had low GFA. Despite the low bulk density (94%), stress-relief annealing resulted in relatively low coercivity (238A/m) in the as-printed samples. Recently, a “record-large” amorphous rotor with intricate 3D geometry was successfully manufactured through the laser AM process, employing the same alloy system (FeSiBCrC). This rotor possesses good soft-magnetic properties (saturation magnetization: 1.29T, coercivity: 510A/m, magnetic susceptibility: 9.17), high hardness (877 HV), and electrical resistivity (178.2 μΩ.cm). Moreover, the amorphization degree was moderate (70%). Consequently, AM presents a promising future technology for the production of large-scale amorphous soft-magnetic components. This chapter focuses on the AM of amorphous Fe-based and Co-based soft-magnetic materials. Among the various AM techniques, powder-bed fusion and direct energy deposition have been applied for this specific purpose. Within this section, an in-depth examination is conducted on these AM processes for amorphous magnetic materials. The chapter also includes an analysis of the research conducted in this field, along with a comprehensive exploration of the advantages and disadvantages associated with each method. © 2025 Elsevier Ltd. All rights reserved.