475 °C Embrittlement in a duplex stainless steel UNS S31803

The susceptibility of a duplex stainless steel UNS S31803 to thermal embrittlement at 475 °C was evaluated by means of mechanical tests (impact energy and hardness), magnetic measurements (hysteresis and thermomagnetic analysis) and scanning electron microscopy. The results show that the material undergoes severe embrittlement and hardening in the first 100 h. The corrosion resistance of the ferrite phase in a 10%HNO3 + 0.05%HF solution deteriorated after 500 h of ageing. The Curie temperature (Tc) was the most sensitive magnetic property to the microstructural changes that promote embrittlement. Tc increases with ageing time due to the progressive reduction of chromium in the Fe-rich matrix during spinodal decomposition.