Additive Manufacturing of Soft Magnetic Bulk Metallic Glasses—A Promising Approach for High-Efficiency Electric Motors

Electric motors play a vital role in various industries ranging from automotive to aerospace to the energy and manufacturing sectors. Directed Energy Deposition (DED) additive manufacturing has emerged as a promising technique to produce geometrically complex components with enhanced functionalities, including inductor cores. Iron-based bulk metallic glasses (BMGs) have garnered attention due to their unique magnetic properties that make them ideal for inductor cores: high magnetic permeability, low coercivity, and reduced hysteresis losses. The lack of long range order and the absence of grain boundaries in BMGs, which is responsible for domain wall pinning, leads to the significantly reduced energy losses. This work utilized DED to optimize processing of an Fe/glass system toward fully dense, net shaped magnetic cores.<br/><br/>Amorphous Fe-based flake (Metglas) was used as DED feedstock. Amorphous content of the resulting builds was assessed via XRD and dominant phases via electron microscopy (BSE,EDS,EBSD). In all cases, the Metglas recrystallized in the printing process due to insufficient cooling rates. Vibrating Sample Magnetometry (VSM) and Magneto Optical Kerr Effect (MOKE) Magnetometry were used to assess bulk and spatially variant magnetic properties of each build. Magnetic saturation of the builds was incredibly high, hovering around 200 emu/g and coercivities varied based on parameters.<br/><br/>Bypassing crystallization is a challenging kinetics problem and requires both novel materials that are compositionally optimized for glass formability and an ideal thermodynamic environment of the cooling process. The DED system is uniquely situated to tackle this challenge by virtue of its fast cooling rates and graded composition functionality.