Thermal aging of ferrite in duplex stainless steels leads to a complex microstructural evolution that can give way to large deleterious changes in mechanical properties. The microstructural evolution mechanisms that happen concurrently are strongly linked to minor changes in composition. By characterizing duplex stainless steels with various compositions over a range of aging conditions, it was revealed that adding a modest amount of Mo to cast austenitic stainless steel (such as changing from grade CF3 to grade CF3M) not only increases the kinetics of spinodal decomposition and Ni-Si-Mn-rich G-phase precipitation, but it also forms a separate Mo-rich phase. At shorter equivalent aging times, Mo segregates from Fe and towards Cr accelerating spinodal decomposition. At longer aging times, Mo enriches in the Ni-Si-Mn clusters before phase separating into an adjoined Mo-rich cluster. These phase changes and precipitation events result in a rather steep drop in fracture and impact toughness. These results will inform the design of similar alloys for use at high temperatures.

双相不锈钢中铁素体的热老化会导致复杂的微观结构演变，从而导致机械性能发生较大的有害变化。同时发生的微观结构演化机制与成分的微小变化密切相关。通过表征在一系列时效条件下具有不同成分的双相不锈钢，发现在铸造奥氏体不锈钢中添加适量的 Mo（例如从 CF3 级变为 CF3M 级）不仅增加了旋节线分解的动力学，而且Ni-Si-Mn 富 G 相析出，但也形成单独的富 Mo 相。在较短的等效时效时间下，Mo 与 Fe 分离并向 Cr 分离，加速了旋节线分解。在更长的老化时间，在相分离成相邻的富钼簇之前，钼在 Ni-Si-Mn 簇中富集。这些相变和析出事件导致断裂和冲击韧性的急剧下降。这些结果将为在高温下使用的类似合金的设计提供信息。