Effect of solution treatment on the transformation behaviour of cold-rolled duplex stainless steels

Abstract The transformation kinetics of the γ → α transition in duplex stainless steels (Feroplug materials) within the solution treatment temperature range of 1050–1250 °C and the accompanying ageing behaviour have been studied by the use of optical/scanning electron microscopy, an image analyzer and magnetic measurements. Increasing the solution treatment temperature increases the amount of ferrite and reduces the anisotropy in the morphology of the ferrite phase in the matrix. In addition, an increase in the ferrite content leads to less chromium and more nickel within the ferrite phase. Ageing at 600 °C and 700 °C showed that the starting time of ferrite transformation (decomposition) is independent of the solution treatment temperature. The main influence of solution treatment temperature is on the overall time required for completion of transformation and the morphology of the secondary austenite ( γ 2 ) formed during transformation. A higher solution treatment temperature produces a ferrite phase of lower chromium content, this increases the time required for the α → γ 2 + σ transformation and produces needle-shaped intragranular γ 2 .