Mechanical Properties of Austenitic-Ferritic Steels
Room Temperature
Duplex stainless steels have significantly higher proof and tensile strength than the austenitic grades. The duplex microstructure in combination with the alloying element nitrogen gives a higher strength. The downside of the high proof and tensile strength is lower elongation values that lead to somewhat lower ductility in comparison to the austenitic grades.
The high tensile strength also implies high fatigue strength. Pulsating tensile fatigue tests shows that the fatigue strength corresponds approximately to the proof strength of the material.
Elevated Temperatures
The duplex grades are, because of their ferrite content, sensitive to the decomposition of ferrite that occurs in the temperature range of 350 to 525 °C. This is called 475°C-embrittlement and lowers the mechanical strength of the material. For this reason it is not recommended that the duplex grades are used in temperatures above 250-300°C.