Effect of cold working and isothermal aging on the precipitation of sigma phase in 2205 duplex stainless steel

A comprehensive understanding of the formation of the sigma phase resulting from the eutectoid reaction (δ → σ + γ2) is required. The kinetics necessary for the eutectoid reaction are closely related to the amount of plastic deformation in DSS. This work investigates the microstructural evolution of the σ phase in a 22Cr–5Ni SAF 2205 DSS after subsequent plastic deformation and isothermal aging. The precipitation of the σ phase resulted from the higher driving force for precipitating intermetallic compounds and the higher diffusion rate of their elements by cold-rolling, as well as the sufficient supply of molybdenum. The maximum amount of σ phase precipitation remarkably increased with an increasing cold deformation, as compared with the non-cold-rolled materials.