Mechanisms of strength and hardening in austenitic stainless 310S steel: Nanoindentation experiments and multiscale modeling

Abstract

Austenitic stainless steels with low carbon have exceptional mechanical properties and are capable to reduce embrittlement, due to high chromium and nickel alloying, thus they are very attractive for efficient energy production in extreme environments. It is key to perform nanomechanical investigations of the role of chromium and the form of the particular alloy composition that give rise to the excellent mechanical properties of steel. We perform nanoindentation experiments and molecular dynamics (MD) simulations of FCC austenitic stainless steel 310S, using established interatomic potentials, and we use a comparison to the plastic behavior of NiFe solid solutions under similar conditions for the elucidation of key dislocation mechanisms. We combine EBSD images to connect crystalline orientations to nanoindentation results, and provide input data to MD simulations for modeling mechanisms of defects nucleation and interactions. The maps of impressions after nanoindentation indicate that the Ni-Fe-Cr composition in 310S steel leads to strain localization and hardening. A detailed analysis of the dislocation dynamics at different depths leads to the development of an experimentally consistent Kocks-Mecking-based continuum multiscale model. Furthermore, the analysis of geometrically necessary dislocations (GND) shows to be responsible for exceptional hardness at low depths, predicted by the Ma-Clarke's constitutive model.

Prediction of Steel Nanohardness by Using Graph Neural Networks on Surface Polycrystallinity Maps

“…The sample preparation, nanoindentation experiments, and microstructural characterization of the low-carbon 310S stainless steel but high in Ni (19 − 22%) and Cr (24 − 26%) content are detailed in [31]. We performed nanoindentation tests using the NanoTest Vantage system designed by Micro Materials Ltd. Hardness measurements were made at room temperature by using a Berkovich diamond indenter tip in a loadcontrolled manner at various depths.…”