Grain Refinement Mechanism of High-Silicon Steel Based on the Addition of Cr and Ni

Fe–6.5Si–2Cr–xNi (x = 4, 8, 12) high-silicon steels with novel chemical composition are fabricated by adding Cr and Ni elements to high-silicon steels. The experimental results show that the microstructures of FeSiCrNi high-silicon steels are gradually refined with the increase in Ni content. In particular, as for Fe–6.5Si–2Cr–12Ni sample, the grains are refined very considerably. Fe–6.5Si–2Cr–12Ni sample comprises a large number of A2 disordered phases, a small number of ordered B2 phases, and a certain number of α-Fe phases. The addition of Ni element inhibits the nucleation of grain boundary ferrite, and thus it contributes to the formation of acicular ferrite with high density of dislocations and high-angle grain boundaries. In addition, the high content of Ni elements leads to slow diffusion of the atoms as well as severe thermal hysteresis in the Fe–6.5Si–2Cr–12Ni sample. This plays an important role in refining the microstructures of Fe–6.5Si–2Cr–12Ni sample. In addition, the intensity of {001}<100> cube texture and {001}<110> rotation-cube texture increases with the increase in Ni content, which makes the Fe–6.5Si–2Cr–12Ni sample have strong λ-fiber texture, α-fiber texture, and γ-fiber texture.