The interaction mechanism between interstitial-substitutional pairs and defects in nitrogen-added austenitic stainless steels

Interstitial-substitutional pairs have been acknowledged to contribute to the increase in the strengths of steels. For further improvements in mechanical properties, their atomic-scale structures and interaction mechanisms with defects are required to be examined. In this study, both high-resolution transmission electron microscopy and atom-probe tomography were used to correlate interstitial-substitutional pairs with defect characteristics in austenitic stainless steels. Three types of defect core structures are identified and associated with their strain fields as well as N-Cr pairs in the N-added steels. It is revealed that N atoms interact elastically with the defects, followed by the formation of N-Cr pairs via the chemical interaction between N and Cr atoms. This insight significantly improves the understanding of the multiple alloying mechanism in metallic materials such as interstitial alloys and high-entropy alloys.