Fabrication of Fe-6.7 wt% Si steel via laser powder bed fusion and investigation of the resulting crystallographic texture

High-Si steel has excellent soft magnetic properties. However, owing to extreme brittleness of high-Si steel, the existing steel manufacturing method, based on rolling, has limitations in the manufacturing of high-performance grain-oriented Fe-Si products. However, high-Si steel with the desired crystallographic texture can be manufactured by utilizing the heat flow characteristics of the laser powder bed fusion (L-PBF) process. In this study, the Fe-6.7 wt% Si steel was fabricated through the L-PBF process, and the formation of the crystallographic texture was examined. Under controlled heat flow during the L-PBF process, the Fe-6.7 wt% Si steel manufactured comprised of columnar grains and exhibited < 001 > crystallographic texture along the building direction. The Fe-6.7 wt% Si steel fabricated via L-PBF exhibited anisotropy in magnetic properties, with high permeability in the build direction owing to the formation of < 001 > crystallographic texture. Under a magnetic field parallel to the build direction, the saturation magnetization was 206 emu/g and the coercive force was 10.2 Oe. To understand the formation mechanism of the crystallographic texture, the melt pool was analyzed in terms of its shape and the angle of the melt pool boundary. The fabricated Fe-6.7 wt% Si steel is composed of three types of melt pools. The grain growth of Fe-6.7 wt% Si steel appeared to depend on the heat flow according to the morphology of the melt pool. A deviation was observed in the grain growth direction due to the presence of the three types of melt pools in the Fe-6.7 wt% Si. The shape of the melt pool is determined by the process variables and scan patterns. Hence, the manufacturing of high-Si steel with desired crystallographic texture and magnetic properties can be achieved via the L-PBF process by controlling the parameters that govern the melt pool shape.