Growth kinetics of secondary austenite in the welding microstructure of a UNSS32304 duplex stainless steel

A thermodynamic and kinetic assessment was made of secondary austenite (gamma(2)) growth in the welding microstructure of a UNS S32304 duplex stainless steel during reheat cycles, between 900 and 1250 degrees C. Calphad-based numerical simulation and analytical electron microscopy characterization analyses were performed. A non-monotonic relationship between the proportion of gamma(2) and reheating temperature was observed, a maximizing gamma(2) fraction being attained at similar to 1050 degrees C. gamma(2) formed at higher reheating temperatures (above similar to 1100 degrees C) displayed an outer shelf rich in chromium and nitrogen and a core region depleted in these alloying elements: in contrast, gamma(2) formed at lower reheating temperatures (tinder similar to 1000 degrees C) displayed almost homogeneous chemical composition. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.