Mitigating core energy losses in Fe-Si alloys fabricated by direct energy deposition through oxide inclusions and abnormal Goss grain growth

Abstract

In traditional electrical steel production oxide inclusions are conventionally perceived as deleterious elements for the functional and structural properties. The present work describes the fabrication of a high silicon content electrical steel alloy (Fe-6.5wt%Si) using directed energy deposition (DED), coupled with oxide inclusions to mitigate core energy losses. Abnormal Grain Growth (ABG) was observed after thermal post-processing at 1000 °C for 24 h (1000–24), together with the creation of oxide inclusions mainly around the grain boundaries. Magnetic properties were assessed through dynamic and quasi-static measurements for both as-printed (AP) and 1000–24 samples. The quasi-static analysis revealed hysteresis losses of 206.9 J/m³ for the AP and 19.02 J/m³ for the 1000–24, with maximum flux densities of 1.295 T and 1.031 T, at the magnetic field of 3000 A/m. Dynamic magnetic analysis demonstrated an improvement of 39.2% in the total core losses of the 1000–24 sample (2088.8 J/m³), compared to the AP sample (3436.9 J/m³). The microstructure of the 1000–24 sample revealed the formation of Goss texture via ABG, ultimately decreasing the static hysteresis loss. Furthermore, an improved electrical resistivity compare to conventional electrical steel alloys was demonstrated at 119 μΩcm for the 1000-24 sample, and 105 μΩcm for the AP sample. This work introduces a promising avenue to minimize core energy losses by incorporating oxide inclusions and ABG Goss texture in additively manufactured soft magneitc components after thermal post-processing.