Effects of grain size and interstitial elements on the Portevin–Le Chatelier effect in austenitic stainless steels

The effects of grain size and interstitial elements (C and N) on the Portevin–Le Chatelier (PLC) effect in two types of Fe-19Cr-13Ni austenitic stainless steels (γ-STSs) were investigated using high-temperature tensile testing with digital image correlation (DIC) analysis. Grain refinement enhanced the yield and ultimate tensile strengths of both steels and reduced the critical strain for dynamic strain aging (DSA). The DSA process related to Cr diffusion was more effectively restricted in the N-enriched atmosphere than in the C-enriched atmosphere, shifting the onset of the serrated flow to higher temperatures. DIC analyses revealed that finer grain sizes decreased the PLC band width and velocity. At 823 K, the higher diffusion rate of Cr in the presence of C induced a transition to a B-type serrated flow, while the addition of N maintained the A-type serrated flow in γ-STS. These findings demonstrate that both grain boundary control and interstitial alloying are crucial for tailoring the PLC band behavior in γ-STS.