Abstract：Because of high coercivity, low permeability and large resistivity, silicon steel is widely used in the manufacture of iron core materials for transformers and various motors. On the basis of silicon steel, the addition of Nb element can improve the electromagnetic properties of silicon steel, and at the same time refine the grains and improve its mechanical properties. The research and application of Fe-Nb-Si ternary alloy is based on the study of ternary phase diagram. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA/WDS) were used to analyze the Fe-Nb-Si ternary system at 1 173 K and 1 073 K. The following phase equilibrium was experimentally investigated. The results show that 11 three-phase equilibrium zones are measured at two temperatures, and three ternary compounds τ2(FeSi2Nb2)、τ5(Fe4Si7Nb4)、τ6(FeSiNb)are found. Themaximum solid solubility of Nb in η phase (Fe5Si3) is about 1.6% (mole fraction, %, the same below) at 1 173 K and 0.5% at 1 073 K. The maximum solid solubility of Fe in αNb5Si3 is about 5.8%at 1 173 K and 4.9% at 1 073 K. The maximum solid solubility of Si in Fe2Nb is 24.3% at 1 173 K and 25.2% at 1 073 K. The maximum solid solubility of Si in μ phase (FeNb) is up to 13.4% Si at 1 173 K and only about 11.3% at 1 073 K. This work improves the phase diagram information of the Fe-Nb-Si ternary system and provides a theoretical basis for the subsequent development of new silicon steel.
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2022, Vol. 27 
