Investigation on Metallurgical Factors Controlling Charpy Impact Toughness in 1Cr21Ni5Ti Duplex Stainless Steel Original Research Article

Based on the fact that toughness degradation occurred in lCr21Ni5Ti duplex stainless steel during slow cooling in a temperature interval of 400–600 °C following brazed welding, a simulated embrittlement treatment was utilized to evaluate its embrittlement tendency. Accumulated experiences have shown that high Ti and Al contents led frequently to severe toughness deterioration. To elucidate this phenomenon, four heats with various Ti and Al contents were prepared in laboratory-scale melts, which were used to investigate the inherent embrittlement nature. The results have shown that 550 °C aging led only to a modest toughness reduction, whereas, aging around 475 °C resulted in ferrite embrittlement, regardless of Ti, Al levels. However, high Ti, Al levels reduced the austenite phase, which, in the case of its inferior shape and distribution due to insufficient hot deformation, failed to resist cleavage-type cracks initiated in the ferrite phase. Increasing hot-forged areas reduction could modify the shape and distribution of austenite, resulting in the enhanced resistance of the austenite to the cleavage-type cracks, which have been confirmed to be beneficial for brittlement suppression of 1Cr21Ni5Ti duplex stainless steel.