In-Situ Observations of Phase Transformations in the HAZ of 2205 Duplex Stainless Steel Weldments

Ferrite (δ)/austenite (γ) transformations in the heat affected zone (HAZ) of a gas tungsten arc (GTA) weld in 2205 duplex stainless steel are observed in real-time using spatially resolved X-ray diffraction (SRXRD) with high intensity synchrotron radiation. A map showing the locations of the δ and γ phases with respect to the calculated weld pool dimensions has been constructed from a series of SRXRD scans. Regions of liquid, completely transformed γ, a combination of partially transformed γ with untransformed δ, and untransformed δ+γ are identified. Analysis of each SRXRD pattern provides a semi-quantitative definition of both the δ/γ phase balance and the extent of annealing which are mapped for the first time with respect to the calculated weld pool size and shape. A combination of these analyses provides a unique real-time description of the progression of phase transformations in the HAZ. Using these real-time observations, important kinetic information about the transformations occurring in duplex stainless steels during heating and cooling cycles typical of welding can be determined.