Micromechanical modeling of hydrogen, dislocation, and short-range ordering interactions for austenitic steels

Le résumé fourni par la source

Abstract Austenitic stainless steels are a hydrogen compatible class of materials but they are expensive and have lower yield strength in comparison to ferritic systems. Decades of experimental investigation have revealed that fracture of these steels in hydrogen is advanced by hydrogen enhanced localized plasticity. In fact, even in cases when the fracture mode is not transgranular, the underlying mechanism is considered to be intense localized slip impinging on grain boundaries or interfaces. Explanations of this localized shear have been sought in the hydrogen-induced reduction of the stacking fault energy (SFE) which can be manifested in slip planarity. However, it is very unlikely for this planarity argument to hold given the small magnitude of the SFE (∼35 mJ m −2 ) in these systems. This work explores the mechanistic role of short-range ordering (SRO) on advancing slip localization as a result of hydrogen-assisted dislocation generation and shielding of dislocation interactions. In view of the absence of relevant experimental data, the mechanics of dislocations breaking through or by-passing SRO regions is investigated through model assumptions drawn from our understanding of the hydrogen/defect interactions. The results indicate that the hydrogen effect on lattice mismatch and dislocation source activation controls the interaction of dislocation pileups with SRO and the associated slip band softening. The promise here is that through proper alloy composition tailoring, these dislocation/SRO interactions can be modulated to control and even mitigate slip localization in hydrogen at a reduced cost.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.