A coupled diffusion-kinetics model for hydrogen thermal desorption spectra from metals

The structural integrity of metals is threatened due to hydrogen interactions with microstructural defects. To investigate this interplay, Thermal Desorption Spectroscopy (TDS) is employed. This work presents a computational framework that couples Fickian transport with McNabb-Foster trapping kinetics. The approach uses a hybrid method and determines initial trap occupancy through thermodynamic equilibrium partitioning for deconvolution. The investigation demonstrates activation energy artifacts resulting from the conventional application of the Kissinger equation. Kinetic convolution is quantified using isoconversional metrics, indicating that peak merging occurs when the kinetic separation between trap populations is less than the depletion width. Finally, a new TDS regime map is introduced, using nondimensional parameters analogous to the Damköhler number (Da) to categorize outgassing as diffusion-limited, reaction-limited, or quasi-equilibrium, illustrating transitions in rate-controlling mechanisms. These findings propose a tool for interpreting hydrogen desorption spectra in structural alloys.