In situ observations of sigma phase dissolution in 2205 duplex stainless steel using synchrotron X-ray diffraction

Synchrotron radiation was used to directly observe the transformation of ferrite, austenite and sigma phases during heating and cooling of 2205 duplex stainless steel. Sigma formed during the initial stages of heating, dissolved as the temperature was increased, and reformed on cooling. The dissolution temperature of sigma was measured to be 985 ± 2.8 °C at a heating rate of 0.25 °C/s, and the kinetics of sigma formation at 850 °C was determined to be slower after dissolving at 1000 °C than before.