Effect of solution treatment temperature on the precipitation kinetic of σ-phase in 2205 duplex stainless steel welds

The effect of the prior solution treatment temperature on the δ-ferrite transformation in 2205 duplex stainless welds after aging at 850 °C has been studied. Microstructural examination showed that the σ-phase and M23C6 chromium carbides precipitate at the δ/γ interfaces and within the δ-ferrite grains. Increasing the solution treatment temperature from 1050 to 1250 °C delays the σ-phase formation and favours the precipitation of intragranular secondary austenite γ2. The simulation of the σ-phase precipitation kinetic in the base metal, HAZ and weld metal, indicates a good agreement between the experimental fitted data and the modified Johnson–Mehl–Avrami model. The results indicate a marked sensitivity of the σ-phase precipitation kinetic to the solution treatment temperature. A high precipitation rate corresponds to a fine grained structure with ferrite enriched in σ forming elements (Cr, Mo).