Influence of the microstructure on the toughness of a duplex stainless steel UNS S31803

The microstructure of a duplex stainless steel UNS S31803 was varied by high temperature treatments (1300°C) followed by different cooling rates. A wide range of microstructures, with differents morphologies and phase proportions, were obtained by this way. Some samples were solution treated at 1000°C and fast cooled after the high temperature treatment. The impact toughness in all conditions were evaluated by reduced size (2.5 mm) Charpy impact tests. The highest toughness was obtained in the samples cooled in furnace from 1300 to 1000°C and then air cooled to room temperature. The microstructure at this condition was very fine with 55.4% of austenite. The lower toughness value was obtained in the water cooled sample, which presented only 17.1% of austenite and large grains of ferrite. The toughness of these and other microstructures was improved by the solution treatment.