Microstructure Control and Magnetic Domain Analysis of Fe-3Si/SUS316 Alloys Fabricated via Additive Manufacturing for Partial Non-Magnetization

Abstract

Partial non-magnetization is one of the technical approaches to control electromagnetism to improve the characteristics of the motor and is achieved by replacing the soft magnetic component of a rotor core with a non-magnetic material. The objective of this study is to realize the partial non-magnetization via the Laser Directed Energy Deposition (L-DED) process. The impacts of applying the intermediate layer on the microstructure and magnetic properties were investigated when Fe-3Si was fabricated on the non-magnetic SUS316. The three types of boundary layers were identified in the sample fabricated without an intermediate layer: the ‘compositional boundary’, where the composition changes from the SUS316 part to the Fe-3Si part; the ‘phase boundary’ where BCC and FCC are mixed; and the ‘microstructural boundary’ consisting of fine grains. The application of Fe-4.5Si-1.2Al as the intermediate layer proved ineffective in suppressing the formation of the compositional boundary. Nevertheless, it was feasible to inhibit the formation of the phase and microstructural boundaries resulting in columnar grains comprising of a single BCC phase which were elongated parallel to the building direction. The magnetic domain structure of these columnar grains was observed using a Kerr microscopy, revealing that the grains oriented <001> to the direction of external magnetization exhibited superior domain change tendencies, similar to Fe-3Si area, despite the existence of the compositional boundary. These results indicated that the deterioration of magnetic properties can be suppressed by introducing an appropriate intermediate layer between the Fe-3Si and SUS316 sections.