Effect of alloying elements on ductile-to-brittle transition behavior of high-interstitial-alloyed 18Cr-10Mn austenitic steels

A study has been made on the effect of alloying elements on ductile-to-brittle transition (DBT) behavior of high-interstitial-alloyed 18Cr-10Mn austenitic steels containing similar amount of N + C. All the steels exhibited a DBT behavior regardless of chemical composition and their DBT temperature (DBTT) was affected by austenite stability and interstitial elements such as N and C. With the exception of a stable austenitic steel, the DBTT measured by Charpy impact tests appeared to be higher than that calculated by an empirical equation depending on N and C. The DBTT of the N alloyed steels was increased with decreasing austenite stability, which is attributed to deformation-induced martensitic transformation occurred at low temperatures, and thus the difference between measured and calculated DBTTs showed a good correlation with austenite stability. At the same content of alloying elements, on the other hand, the N + C alloyed steel had a lower DBTT than the N alloyed steel, presumably because the combined addition of N + C enhances the metallic component of interatomic bonds and also lower N content contributes to the decrease of DBTT.