Phase-Field Insights into Hydrogen Trapping by Secondary Phases in Alloys

Abstract

Solid-state hydrogen storage is the best choice for balancing economy and safety among various hydrogen storage technologies, and hydrogen storage in the secondary phase might be a promising solid-state hydrogen storage scheme. In the current study, to unmask its physical mechanisms and details, a thermodynamically consistent phase-field framework is built for the first time to model hydrogen trapping, enrichment, and storage in the secondary phases of alloys. The hydrogen trapping processes, together with hydrogen charging, are numerically simulated using the implicit iterative algorithm of the self-defined finite elements. Some important results are attained: 1. Hydrogen can overcome the energy barrier under the assistance of the local elastic driving force and then spontaneously enter the trap site from the lattice site. The high binding energy makes it difficult for the trapped hydrogens to escape. 2. The secondary phase geometry stress concentration significantly induces the hydrogen to overcome the energy barrier. 3. The manipulation of the geometry, volume fraction, dimension, and type of the secondary phases is capable of dictating the tradeoff between the hydrogen storage capacity and the hydrogen charging rate. The new hydrogen storage scheme, together with the material design ideology, promises a viable path toward the optimization of critical hydrogen storage and transport for the hydrogen economy.

Local Hydrogen Measurements in Multi-Phase Steel C60E by Means of Electrochemical Microcapillary Cell Technique

“…Often, there is an interaction of both HEDE and HELP mechanisms, which results in mixed fracture patterns with both inter-and transgranular morphologies (Figure 1C). Once diffusive hydrogen has been absorbed into the material, it either occupies interstitial lattice sites (diffusive hydrogen H) or becomes trapped at energetically favorable microstructural inhomogeneities (HT) such as dislocations, grain boundaries, vacancies, or phase boundaries [24][25][26][27]. Since H remains mobile at ambient temperature, it is generally considered the cause of hydrogen embrittlement.…”

The Effects of Electrochemical Hydrogen Charging on Charpy Impact Toughness and Dry Sliding Tribological Behavior of AISI 316H Stainless Steel

“…These traps are various defects of the metal crystal lattice (e.g., dislocations, vacancies, substitution atoms, precipitates, inclusions, etc.) showing the existence of internal stresses in their surroundings [11][12][13][14][15][16][17][18]. Thus, there are significant differences in the HE resistance among different classes of metallic materials taking into account not only their varying chemical compositions but also their various processing and service conditions influencing their crystallographic structures and phase composition characteristics.…”