Structure and properties of the heat-affected zone of duplex steels welded joints

Influence of the secondary austenite gamma(2)-precipitation in a heat-affected zone of welded joints of duplex steels, on hardness and corrosion resistance, have been analysed. The secondary austenite was created as a product of ferrite decomposition alpha -> gamma(2) as an effect of the welding thermal cycle and an aging following the welding process. Correlation of the thermal Cycle, gamma(2)-phase morphology, kind of precipitations and hardness, as well as a corrosion resistance were described. Thermal cycle has a significant influence on the transformation alpha -> gamma(2), and morphology of the created gamma(2)-phases. The main mechanism of the secondary austenite creation is the diffusive transformation, as a result of which the Widmanstatten structure is formed. The increase of the gamma(2)-phase quantity in the tested steel heat-affected zone causes an essential influence of the joint hardness and corrosion resistance. (c) 2005 Elsevier B.V. All rights reserved.