Duplex Steels: Part I: Genesis, Formation, Structure

The ferritic-austenitic duplex steels are equipped with a mechanical-technological combination of properties, which is advantageous compared to the features of stainless completely ferritic or completely austenite steels. The duplex steels crystallize by fully ferritic or ferritic-austenite solidification with the austenite precipitation due to the solid solution reactions during the further cooling. To adjust the ferrite-austenite ratio, the steels must be heat treated by temperatures above the field of precipitation stability, followed by water quenching. The temperature and the time of the heat treatment effect the element distribution according to their higher solubility in the ferritic or austenitic phases. The typical microstructure of the duplex stainless steels can only be realized due to deformation and recrystallisation processing.