Explicit Incorporation of Dislocation Pipe Diffusion Mechanism into the Sofronis–McMeeking Hydrogen Transport Framework

Hydrogen permeation experiments in austenitic stainless steels (e.g., [1]) show that microstructural features—especially dislocation density—strongly modulate transport, leading to large scatter in reported diffusivity and permeability. Yet widely used hydrogen transport models, such as the Sofronis–McMeeking framework, treat dislocations only as reversible traps rather than fast diffusion pathways and therefore fail to capture microstructure–property relationships, leading to the need of ad-hoc, sample-specific parameter tuning. This paper presents a thermodynamically consistent, microstructure-explicit framework that augments the hydrogen transportation model by explicitly introducing dislocation-assisted pipe diffusion and reversible trapping. Validation is performed against permeation experiments of 316L stainless steel samples fabricated by laser powder bed fusion (L-PBF) and subjected to different post-built heat treatment conditions. Dislocation densities and their spatial distribution are inferred from EBSD (grain size/misorientation metrics) and analytical yield-strength analysis, then used as simulation inputs. With minimal calibration to a small data subset, the model reproduces the large variation in measured permeability across a 350 ^o C-550 ^o C temperature range and the sensitivity to the dislocation densities. The results demonstrate that explicitly accounting for dislocation-assisted pipe diffusion is essential to reproduce microstructure-based hydrogen transport behavior, providing a mechanistic basis for assessing hydrogen embrittlement in austenitic steels.