Ageing of cast duplex stainless steels (DSS) is attributed to the decomposition of the ferrite: spinodal decomposition and precipitation of G-phase particles. This leads to an increase in hardness and a decrease in Charpy toughness. According to the literature, spinodal decomposition is accepted to play a major role on the hardening even if the role of G-phase precipitation on mechanical properties is still not clear. This work links microstructural characterization performed using atom probe tomography to micro-hardness of the ferrite for a wide variety of duplex steels (from cast steels with and without Mo to lean steels) aged under different conditions. An attempt to quantify the contribution of both spinodal decomposition and G-phase precipitation is made by applying linear and square superposition principle of Ardell, Orowan and a modified BKS models. The models used are shown to give an excellent estimation of the experimental values of the hardness increase of the ferrite of the cast and lean steels for a wide range of composition and temperature. This work shows that, conversely to what is said in the literature, spinodal decomposition is not systematically the main contributor to hardening.

铸造双相不锈钢（DSS）的时效归因于铁素体的分解：旋节线分解和G相颗粒的沉淀。这导致硬度增加和夏比韧性降低。根据文献，即使尚不清楚G相沉淀对机械性能的作用，也认为旋节线分解对硬化起主要作用。这项工作将使用原子探针层析成像技术进行的显微组织表征与在不同条件下进行时效的多种双相钢（从含钼和不含钼的铸钢到贫钢）的铁素体的显微硬度联系起来。利用Ardell的线性和平方叠加原理，试图量化旋节线分解和G相降水的贡献，Orowan和改良的BKS模型。结果表明，所使用的模型可以很好地估算各种成分和温度范围内铸钢和贫钢的铁素体硬度增加的实验值。这项工作表明，与文献中所说的相反，旋节线分解并不是系统地导致硬化的主要因素。