针对0.46%Si (质量分数)和1.36%Si 2种40%超高铬1.5%高碳双相钢，采用OM、SEM、EPMA、XRD及化学分析等方法研究了2种钢的成分、铸态组织和凝固过程，以及固溶处理后钢的组织和相结构的变化。结果表明，2种钢铸态组织均由γ奥氏体、σ相和M₂₃C₆组成。Si含量为0.46%时，先析出树枝状δ铁素体，随后为(δ+M₂₃C₆)_eutectic、γ_peritectic，最后为(γ+M₂₃C₆)_eutectic，其中δ铁素体在后续冷却过程中共析转变为(γ₂+σ)_eutectoid。Si含量为1.36%时，δ铁素体量增加导致σ相明显增加，包晶γ变为断续不规则形状，无(γ+M₂₃C₆)_eutectic形成。固溶处理后，0.46%Si和1.36%Si 2种超高铬高碳双相钢均由铁素体、奥氏体和M₂₃C₆型碳化物三相组成，但Si含量的增加，明显提高了组织中铁素体的含量和连续性。实验结果还表明，Si使超高铬高碳钢的硬度、抗拉强度和断裂韧性有所增加，对耐蚀性影响不明显，但使耐磨性能略有下降。

Duplex stainless steels have excellent corrosion resistance, but its insufficient wear resistance limits its application scope. Therefore, alloying of duplex stainless steels to form hard phases, such as carbides, becomes one of the important research directions to enhance their wear resistance keeping their good corrosion resistance. Specifically, carbides are considered as an ideal hard phase to strengthen Fe-Cr-C alloys, where their types, hardness, volume fraction, morphology, size, spacing and interconnecting feature are the important factors affecting the wear resistance of the alloys. It has been shown that, Si as an alloying addition can modify the carbide precipitates in type, phase morphology and distribution in Fe-Cr-C alloys, having an obvious influence on their wear and corrosion resistance as well as their mechanical properties. In this work, the microstructure and properties of two types of ultra-high chromium (40%, mass fraction) and high carbon (1.5%) duplex stainless steels with different concentrations of Si (0.46% and 1.36%) are investigated. The composition, as-cast microstructure and solidification process as well as the changes in the microstructure, phase structure after solution treatment were studied by chemical analysis, OM, SEM, EPMA and XRD. The mechanical properties including hardness, tensile strength, fracture toughness, corrosion resistance and wear resistance have been tested correspondingly. It is revealed that, both the two kinds of duplex stainless steels have a constitution of three phases in as-cast state, i.e. γ phase, σ phase and M₂₃C₆. During the solidification process of the steel with 0.46%Si, δ ferrite dendrite forms at the beginning, followed by eutectic (δ+M₂₃C₆), peritectic γ, and finally eutectic (γ+M₂₃C₆), in which the δ phase transformed into eutectoid (γ₂+σ) in the subsequent cooling process. For the duplex stainless steel with 1.36%Si, the increase of δ ferrite amount is observed leading to obviously increased content of σ phase, the morphology of peritectic γ becomes intermittent and irregular shape, and no eutectic (γ+M₂₃C₆) forms. After solution treatment, the two kinds of steels are composed of ferrite, austenite and M₂₃C₆ type carbide. Note that, the volume fraction and continuity of α ferrite are promoted obviously by increasing Si content from 0.46% to 1.36%. The Si addition slightly improves the hardness, tensile strength and fracture toughness of the duplex stainless steel, while has little effect on the corrosion resistance and slightly reduces the wear resistance.