Selective Laser Melting of a Fe-Si-Cr-B-C-based Complex-Shaped Amorphous Soft-Magnetic Electric Motor Rotor with Record Dimensions

A record large amorphous rotor bearing an intricate 3D-geometry is produced through additive manufacturing via selecting laser melting using a powder of a bulk metallic glass-forming composition of the Fe-Si-Cr-B-C system. Not only does this technique overcome the technical limitations characteristic of casting processes for amorphous alloys, but also the possibility to print complex 3D geometries is expected to greatly facilitate the channelling of the magnetic flux, when such component is used as a rotor in an electric machine. The rotor is characterized in comparison to the powder material as well as the as-spun ribbon using complementary techniques, including synchrotron x-ray diffraction, calorimetry, scanning and transmission electron microscopy as well as room temperature ferromagnetic and hardness testing. The rotor has extraordinarily high values of hardness (877 HV), high electrical resistivity (178.2 µΩ cm) and remarkable high magnetic susceptibility (9.17). This latter feature leads to a better magnetic response in the presence of an external magnetic field evidenced by a faster approach to saturation. The coercivity is relatively small (0.51 kA/m) and the magnetic saturation relatively high (1.29 T). In addition, a large anisotropic effect on the magnetization response in connection with partial crystallization in the melt pool areas is assessed experimentally.