6533b7ddfe1ef96bd1273b43

RESEARCH PRODUCT

Additive manufacturing Processing and characterization of Fe-Si soft magnetic alloys

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Iron silicon (Fe-Si) alloys, also named silicon steels, are the most widely used owing to their excellent soft magnetic properties and economic costs. As electronic devices become diversified and automated, it is urgent to develop high-performance soft magnetic alloys with good reliability. For functional soft magnetic alloys, the SLM technique shown the potential to manufacture soft magnetic components directly from raw materials, such as the rotor and stator of the motor. In order to explore and develop new routes for manufacturing Fe-Si alloys, the investigation into the microstructures and properties of SLMed Fe-Si alloys from pre-alloyed powders was presented in this work. The most important finding in this work is listed in the following.After adopting a series of experiments and characterization, under optimal linear energy density, SLMed Fe-3 wt.%Si specimens with good surface roughness, low relative porosity, and without cracks can be obtained. The microstructure of the SLMed parts exhibited a typical columnar structure with an oriented growth of building direction. The SLM-produced Fe-3wt.%Si alloy presented a single Fe-bcc phase, a {100} cubic texture in our study, i.e. a texture along the building direction (BD). Hence, in the printing coordinate system, the three directions of X, Y, and Z are contained in the axis that is easy to be magnetized, the alloy had isotropy magnetic properties at these three measured directions (X, Y, and Z). The elongation at break (EL) of the specimen reached 8.8%, the average ultimate tensile strength (UTS) and Yield strength (YS) are 562 Mpa, 445 Mpa, respectively. A mixed-mode of ductile and brittle failure is the main rupture mechanism for SLMed Fe-3wt.%Si alloy. A series of annealed treatments with different dwell times and annealed temperatures were adopted. The results show that annealing conducted at 1000 °C for 3 h, caused instead a marked grain growth. As the dwell time increased to 5h, by the comparison of the AT1000/3h sample, the grains almost did not grow further significantly. The magnetic properties of the SLMed Fe-3wt.%Si magnet could be comprehensively enhanced, attributing to grain grew and stress release via submitted annealing temperature-time combination appropriately.To investigate the effects of silicon content on the microstructures and properties of SLMed silicon steels, the pre-alloyed with silicon contents of 3.5wt.%, 4.5wt.%, and 5.5wt.% were selected. Experimental results revealed that with the increase of silicon content, the micro segregation of silicon in SLMed samples becomes more serious, especially at the boundary of the molten pool. The relative maximum permeability increases with the increase of silicon content, both coercivity and power losses decrease with the increase of silicon content. The saturation magnetic induction exhibits a slightly decreasing trend while the remanence is shown an increasing trend. The increase of Si content has a positive effect on the strength while damages the ductility of the SLMed silicon steel, resulting in the highest microhardness and the highest average UTS while the lowest average within these three types of silicon steels. Brittle fracture is the dominant fracture mechanism for the present three types of SLMed silicon steels. Both the SLMed as-built and annealed samples for three types of silicon steels are characterized by a single bcc-phase, no obvious phase transformation is presented during annealed treatment. The annealed treatment resulting in grain growth and stress relief for three types of silicon steels, as such, their comprehensive magnetic properties are also improved. The annealing behavior is not dramatically altered by variations in alloy chemistry of Si content.