Complex magnetic and microstructural investigation of duplex stainless steel

Heat treatment induced microstructural processes were studied by different non-destructive magnetic methods in the present work. A commercial SAF 2507 type superduplex stainless steel was investigated. This alloy contains about 40% ferrite and 60% austenite phases in its initial condition. The ferrite phase is not stable, therefore it can decompose to sigma phase and secondary austenite due to heat treatment. All the mechanical, corrosion resistance and magnetic properties are strongly influenced by the microstructural changes. This study had two aims: to understand better the kinetics of the ferrite decomposition process and to study the application possibilities of the applied magnetic measurements. The results, which were supported by electronmicroscopic method (electron back scattered diffraction, EBSD), help us to understand better the microstructural changes in duplex stainless steels caused by heat treatment.