This study compares the hydrogen embrittlement susceptibility of a Fe-30Mn-8Al-1.2C austenitic low-density steel aged at 600 °C for 0 (RX), 1 min (A1) and 60 min (A60), each exhibiting varying sizes and distributions of nano-sized κ-carbides. Slow strain rate tests were conducted to assess hydrogen embrittlement susceptibility, while thermal desorption analysis was applied to investigate hydrogen trapping behaviors. Fracture surface analysis was employed to discuss the associated failure mechanisms. The results suggest that nano-sized κ-carbides with sizes ranging from 2–4 nm play a crucial role in mitigating hydrogen embrittlement, contrasting with the exacerbating effect of coarse grain boundary κ-carbides. This highlights the significance of controlling the sizes and morphology of precipitates in designing hydrogen-resistant materials.

An ultra-high strength martensitic steel, strengthened by the dual-precipitation of NiAl and M2C nano-particles, has been successfully developed and produced on an industrial scale. It has achieved a remarkable tensile strength of 2467 MPa and exhibited ductility approaching 10%. The precipitation configurations of NiAl and M2C nano-particles during ageing at 510 degrees C for durations ranging from 0.5 to 10 h were characterized using atom probe tomography. The results indicate that the preferential precipitation of NiAl, facilitated by minimal lattice misfit and low interfacial energy, promotes the uniform nucleation of M2C particles within the matrix while restricting their growth. As a result, both types of precipitates maintain a high number density. With increasing ageing time, the distribution density of the precipitates decreases, their size increases and the increase in yield strength gradually decreases. Furthermore, the addition of element cobalt effectively reduces the diffusivity of other major alloying elements, synergistically inhibiting the growth of NiAl and M2C particles. The dual precipitates co-configuration provides a substantial hardening effect (1046 MPa at 510 degrees C for 220 min) compared to the individual hardening effect of M2C observed in AerMet100 steel.

High-nitrogen steels (HNS) have attracted raised attention due to their exceptional mechanical properties, corrosion resistance and wear resistance. These properties have led to increased applications in energy production, transportation, pulp and paper, oil and gas, chemical industries and so forth. To foster scientific and technical exchanges between experts from the steel industry, research organizations and end-users concerning this specific steel category, the International Conference on High Nitrogen Steels was initiated in Lille (France) in 1988, continued in Aachen (Germany) in 1990, Kiev (Ukraine) in 1993, Kyoto (Japan) in 1995, Helsinki/Stockholm (Finland/Sweden) in 1998, Chennai (India) in 2002, Schaffhausen (Switzerland) in 2003, Ostend (Belgium) in 2004, Jiuzhaigou Valley (China) in 2006, Moscow (Russia) in 2009, Chennai (India) in 2012, and Hamburg (Germany) in 2014. The 13th International Conference on High Nitrogen Steels (HNS2021) was held in a hybrid format on 14th Sep. 2021 in Shanghai due to COVID-19-related travel restrictions. The conference was chaired by Prof. Han Dong (Shanghai University, China) and Prof. Guocai Chai (Sandvik Materials Technology AB/Linköping University, Sweden). The conference program comprised 8 plenary speeches and 23 oral presentations delivered by experts from research institutes, universities, and companies from over 11 countries. Prof. Han Dong opened the conference with a speech on “Look at high nitrogen austenitic stainless steels at present”. The conference featured four parallel sections covering topics: nitrogen alloying mechanisms, mechanical properties, processing and production of HNS, and their applications and in-service properties. The conference attracted over 400 online participants. This special section of Steel Research International publishes 7 highlighted works presented at HNS2021, following the journal’s regular review process. Prof. Guocai Chai presents “Roles of Nitrogen on TWIP in Advanced Austenitic Stainless Steels”. The article discusses the effect of nitrogen on deformation mechanisms at cryogenic temperature and the resulting mechanical and magnetic properties. (see front cover and article 2200359). Prof. Toshihiro Tsuchiyama reports on “Nitrogen-Enhanced Temperature Dependence of Grain Refinement Strengthening in Austenitic Stainless Steel”. The work reveals that nitrogen significantly enhances the increment of the Hall-Petch coefficient at low temperatures in high-N-containing 316L steel. As explained by the pileup model, nitrogen contributes substantially to raising the critical grain boundary shear stress and enhancing the grain boundary bonding force at low temperatures. (See back cover and article 2200428). Prof. Zhouhua Jiang and Prof. In-Ho Jung report on “Thermodynamics of Nitrogen in Molten Fe–Cr–Mn–C–N Alloys” by using the Modified Quasichemical Model with the consideration of short-range ordering. They determined a set of new self-consistent binary and ternary model parameters for the Fe-Cr-Mn-C-N solution and applied them to predict the N solubility in this multi-component molten alloys, which is vital for the process optimization of high N stainless steels, ferritic stainless steels, TWIP steels, etc. (see article 2200510). Prof. Hua-Bing Li presents “A Promising Pressurized Duplex Manufacturing Route of High Nitrogen Stainless Steel“ by incorporating the pressurized induction melting (PIM) process to fulfil nitrogen alloying, deoxidation and desulfurization and pressurized electro slag remelting (PESR) process to further desulfurize, remove large-size inclusions and elevate solidification quality. High nitrogen stainless bearing steel 30Cr15Mo1N (DIN 1.4108) has been successfully manufactured and demonstrated improved mechanical and corrosion properties compared to the single-stage PIM process (see article 2200321). Prof. Mei Zhang reports “Hot Deformation Behavior and 3D Processing Maps of Mn18Cr18N Steel”, which established a 3D processing map of Mn18Cr18N steel based on controlled hot deformation parameters using a Gleeble-3500 thermomechanical simulator and dynamic materials model. The optimum hot working temperature and strain rate domains 1000-1150°C/0.002-0.1 s 1 with effective dynamic recrystallization have been proposed (see article 2200358). Prof. Wei Peng presents “Insights into the Impact Behavior and Deformation Substructure Evolution of the N-Bearing QN1803 and 304 Stainless Steels”. The 0.26%N bearing QN1803 austenitic steel demonstrated a pronounced ductilebrittle transition temperature, which has higher impact energy than 304 at a high-temperature domain of 0-100°C. Its postponed fracture occurrence was attributed to the promoted fault growth in N-enriched zones. At low temperatures, the QN1803 has low stacking fault energy and reveals high local shear at the stacking faults, leading to local fracture initiation (see article 2200508). Prof. Ke Yang reviews high-nitrogen nickel-free stainless steel as an attractive biomedical metallic material with high strength, high fatigue resistance, high pitting corrosion resistance and H. Dong, X. Guo School of Materials Science and Engineering Shanghai University 200444 Shanghai, China E-mail: donghan@163.com; xiaofei_guo@shu.edu.cn G. Chai Research, Alleima AB (Sandvik group earlier) 81181 Sandviken, Sweden E-mail: guocai.chai@alleima.com G. Chai Engineering Material Linköping University 58183 Linköping, Sweden E-mail: guocai.chai@liu.se

The effects of cold rolling reduction rates and recrystallization annealing temperature on the microstructure, texture, and anisotropic properties of high-strength low-alloy (HSLA) steel were investigated using scanning electron microscopy and electron backscatter diffraction. The results revealed that the constituents of recrystallized, substructured, and deformed structures were strongly affected by cold rolling reduction rates ranging from 33.3% to 66.7% and recrystallization temperatures ranging from 780 to 840 °C. At an annealing temperature of 820 °C, when the cold rolling reduction rate was 33.3%, HSLA steel exhibited a low percentage of recrystallization, with cubic, γ-linear, rolled, and Z-texture (the texture at Euler angles φ1 = 30° and Φ = 20°–30°) structures. The rolled texture and Z-texture increased the strength anisotropy and disappeared at high cold rolling reduction rates. When the annealing temperature was increased from 780 °C to 820 °C, the proportion of recrystallized grains increased, the rolling texture disappeared, and grain orientation gradually gathered in the cubic texture and γ line texture, resulting in low anisotropy of strength. At an annealing temperature of 840 °C, the deformation of the grain disappeared; however, the anisotropy increased compared to annealing at 820 °C because of the formation of a new texture of {001}<−1–20>.

The microstructure, mechanical properties and resistance to hydrogen-assisted degradation of a medium man-ganese stainless steel (Fe-0.17C-10Mn-18Cr-5Ni-0.9V-0.26 N, in wt. %) were investigated. The investigated steel was 65% cold rolled and subsequently annealed at 1000 degrees C for 3 min to promote a very fine-grained austenitic microstructure of-1.3 & mu;m with various V/Cr-rich precipitates in the size range of 20-400 nm. This steel took up 2.48 ppm hydrogen during in-situ immersion slow strain rate tensile (SSRT) testing at a strain rate of 10-6 s � 1 in 5% NaCl. Insignificant changes in its strength and ductility values were observed, which dem-onstrates a high resistance to hydrogen-assisted degradation. The analysis of thermal desorption spectroscopy (TDS) curves of the SSRT specimens revealed that hydrogen uptake occurs on irreversible hydrogen traps (precipitates), which inferred from the corresponding high temperature desorption peaks. Transmission electron microscopy conducted on interrupted tensile samples revealed the formation of nano-deformation twins of-20 nm, which explains the outstanding strain hardening behavior. The findings demonstrate an excellent hydrogen trapping ability due to multiple types of precipitates in the fine-grained austenitic microstructure, and an outstanding strength-ductility balance (yield strength: 600 MPa, ultimate tensile strength: 975 MPa, total elongation: >45%) that is explained by deformation-induced nano-twins. The synergetic effects of various types of precipitates, fine grain size and deformation mechanism on the resistance to hydrogen-assisted degradation and mechanical behavior are discussed.

In this study, the effect of hydrogen on dislocation and twinning behavior along various grain boundaries in a high-manganese twinning-induced plasticity steel was investigated using an in situ micropillar compression test. The compressive stress in both elastic and plastic regimes was increased with the presence of hydrogen. Further investigation by transmission electron backscatter diffraction and scanning transmission electron microscope demonstrated that hydrogen promoted both dislocation multiplication and twin formation, which resulted in higher stress concentration at twin–twin and twin–grain boundary intersections.

Hydrogen embrittlement (HE) sensitivity of S690QL structural steel and X80 pipeline steel in both as delivered and welding simulated heat treatment conditions have been investigated by slow strain rate test (SSRT) with in-situ hydrogen charging. Both investigated steel grades show low strength losses, however, high ductility losses, represented by losses in total elongation and area reduction after in-situ hydrogen charging at a constant current density. The resulting diffusive hydrogen contents after charging are associated with the material microstructure, which are 2-3 ppm for S690QL and 1-2 ppm for X80. The lath martensite dominated microstructure in heat- treated S690QL specimens revealed extremely high HE sensitivity as demonstrated by fracture occurring within the elastic deformation regime. Hydrogen induced damage was found associated with the brittle nature of the quenched lath martensite, the severe grain coarsening, and the large fraction of high angle grain boundaries. The X80 pipeline steel reveals a transition from granular bainite dominated microstructure to lath bainite/martensite dominated microstructure after welding simulated heat treatment. The uptake of diffusive hydrogen during the in-situ charging process of X80 specimens was less compared to S690QL specimens, which was also desorbed at higher temperatures as characterized by hydrogen thermal desorption analysis. The results sug-gest a controlled bainitic/martensitic microstructure transformation with designed precipitation hardening would contribute to both strength enhancement and the suppression of hydrogen mobility.

The influences of hydrogen on the mechanical properties and the fracture behaviour of Fe-22Mn-0.6C twinning induced plasticity steel have been investigated by slow strain rate tests and fractographic analysis. The steel showed high susceptibility to hydrogen embrittlement, which led to 62.9% and 74.2% reduction in engineering strain with 3.1 and 14.4 ppm diffusive hydrogen, respectively. The fracture surfaces revealed a transition from ductile to brittle dominated fracture modes with the rising hydrogen contents. The underlying deformation and fracture mechanisms were further exploited by examining the hydrogen effects on the dislocation substructure, stacking fault probability, and twinning behaviour in pre-strained slow strain rate test specimens and notched tensile specimens using coupled electron channelling contrast imaging and electron backscatter diffraction techniques. The results reveal that the addition of hydrogen promotes planar dislocation structures, earlier nucleation of stacking faults, and deformation twinning within those grains which have tensile axis orientations close to <111>//rolling direction and <112gt;//rolling direction. The developed twin lamellae result in strain localization and micro-voids at grain boundaries and eventually lead to grain boundary decohesion.

The hydrogen embrittlement (HE) behavior on a Fe-22Mn-0.6C twinning-induced plasticity (TWIP) steel was investigated by tensile tests with in-situ scanning electron microscope observation combined with electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI) techniques. The tensile test specimens were cathodically pre-charged with hydrogen for 0, 50, 150, and 300 h, which accumulatively reduced the mechanical properties and induced a ductile-to-brittle fracture transition. The threshold of hydrogen content to trigger this ductile-to-brittle transition was further determined by combined thermal desorption spectroscopy (TDS) analysis and theoretical hydrogen diffusion calculation. During the tensile tests, intergranular secondary cracks were observed on the gauge surfaces of the specimens with pre-charged hydrogen. The low angle grain boundaries (LAGBs) exhibited better resistance to both crack initiation and propagation compared with high angle grain boundaries (HAGBs). In addition, the stress concentration together with the hydrogen effect on grain boundaries intersected with deformation twins are proposed as the reasons for the crack initiation and propagation.Y

In this study, three catalysts (BC-Zn, BC-HP and BC-Na) were prepared by pyrolyzing corn stalk biomass with ZnCl2, H3PO4 and NaOH acting as activator. We compare and summarize the structure and electrocatalytic activity of these carbon materials for oxygen reduction reaction (ORR). A highperformance doped carbon catalyst (BC-Na) with a BET surface area of up to 1337.27 m g was prepared by using NaOH as an activating agent. For ORR in alkaline media, BC-Zn exhibited a more negative shift of -0.42 V (vs Hg/HgO) in contrast to BC-HP (-0.31 V) and BC-Na (-0.31 V). Even though BC-Na showed a negative ORR onset potential (E=-0.21 V) in comparison with Pt/C (E=0.09V), its current density reached up to 5.72 mA·cm, which is much higher than Pt/C (3.25 mA·cm). It is supposed that the excellent electrocatalytic property of BC-Na originated from the combined effect of high specific surface area and N doping. The low-cost and simple approach used in study provides a straightforward route for the preparation of ORR electrocatalysts from biomass.

Effective treatment of 2,4-dichlorophenol (2,4-DCP) in wastewater is essential, as it could pose great threat to the environment. A hydrothermal biochar (hydrochar) was used to assist the electrochemical oxidation treatment of 2,4-DCP. The removal of 2,4-DCP using hydrochar in anode and cathode area with and without proton exchange membrane (PEM) under 3-9 V of electrolysis was investigated. Enhanced 2,4-DCP degradation in the anode area was achieved compared with the adsorption or electrolysis alone. The highest 2,4-DCP removal (similar to 76%) was obtained using the hydrochar in the anode area with PEM under 9 V. The mechanism for the 2,4-DCP removal during the electrolysis included adsorption by hydrochar and electrochemical degradation by the reactive oxygen species (ROS) generated by the electrode as well as the persistent free radicals (PFR) on hydrochar. The center dot OH produced from anode was the predominant ROS contributing to the 2,4-DCP degradation under 9 V of electrolysis. (C) 2020 Elsevier Ltd. All rights reserved.

This paper discusses the avoidance of hydrogen embrittlement (HE) in a medium manganese stainless steel X20CrNiMnVN18-5-10. We adopted a HE-mitigation strategy that relies on improving its intrinsic resistance to hydrogen by adjusting an ultrafine microstructure (∼1.3 µm) containing a significant amount of nano-sized V- and Cr-based precipitates in the size range of 20 - ≥200 nm. The precipitation state was characterized using a high-resolution scanning transmission electron microscope. Slow strain rate tests at a strain rate of 10−6 s−1 were conducted on specimens with/without hydrogen pre-charging to evaluate the HE susceptibility. Thermal desorption analysis was applied to explore the hydrogen trapping behavior in cold-rolled, annealed and hydrogen pre-charged states. Hydrogen uptake and hydrogen desorption behaviors show a dependence on the size of precipitates. It is remarked that the large precipitates trap a larger amount of hydrogen and show a higher temperature desorption peak than the small precipitates do. The high-temperature hydrogen desorption peaks (>400 °C) indicate that the observed nano-sized precipitates provide irreversible trapping sites, where hydrogen uptake occurs. The investigated steel X20CrNiMnVN18-5-10 demonstrates an enhanced intrinsic resistance to HE in comparison to medium and high manganese as well as stainless steels. The findings suggest that microstructure engineering with sufficient number of hydrogen traps in an ultrafine-grained microstructure is an appropriate HE mitigation strategy that allows designing hydrogen-resistant advanced high strength steels.

The microstructure of Fe-Mn-Al-C alloys is largely influenced by heat treatment, which leads to different mechanical properties. The current work investigated the microstructure evolution in the austenite zone in a low density steel Fe-10Mn-5.5Al-0.25C at the heat treatment temperature range of 850 °C–1000 °C. The microstructure features have been characterized by SEM, TEM. The results indicate that the soaking temperature has great influence on the room-temperature mechanical properties, even promotes austenite-to-martensite transformation at 1000 °C heat treatment. The increased temperature and austenite zone fraction degrade the stability of austenite, whilst the small B2 phase shows no detrimental effect on mechanical properties. The product of tensile strength and elongation increases from 28 to 50 GPa% is due to multiple deformation mechanisms with austenite zone fraction increased. And the transformed martensite at 1000 °C significantly decreases the mechanical properties. So, the improved mechanical properties maybe attributed to the coordination function of dislocations pile-up and cut through the B2 phase, and strengthened TWIP effect as heat treatment temperature below 1000 °C.

The influence of shear and laser cutting on hydrogen embrittlement of a hot-rolled Fe-18Mn-0.4C-1.2Al-1.8Cr TWIP (twinning induced plasticity) steel sheet in 3 mm thickness was investigated by hydrogen pre-charging and subsequent slow strain rate tests. Due to the severe plastic deformation during shearing, the ductility of the shear-cut specimen was significantly reduced in tensile test compared to the laser-cut specimen. After hydrogen pre-charging, the laser-cut specimen exhibited less susceptibility to hydrogen embrittlement than the shear-cut specimen. The fractographic analysis revealed that the shear-affected zone acted as crack initiation site during tensile test, which exhibited a flat fracture zone with high stress triaxiality. In hydrogen-charged condition, the flat fracture zone transited from large primary dimples to the mixed features with dimples and quasi-cleavage features.

Complex carbide precipitates in a quenched and tempered low alloy Cr-Mo-V steel after long-term aging at 650 °C for 13,000 h and 30,000 h were investigated in this study. The mass fraction and sizes of precipitates were quantified by electrolytical extraction technique. The types of precipitate were further studied by combined X-ray diffraction and transmission electron microscopy with selected area electron diffraction and energy dispersive spectrometry. A series of carbide precipitates, namely MC, M7C3, M6C, and M2C, were found existing in the near-equilibrium state. The precipitate sequence of these carbides was identified as MC + M7C3 + M2C → MC + M2C + M7C3 + M6C → MC + M7C3 + M6C. It was clarified that the stable phases for the investigated steel aged at 650 °C were composed of MC, M7C3, and M6C. For the first time, the in-situ transformations of M2C to M6C and M7C3 to M6C were directly observed. It was also observed that the nucleation site of the M6C was located at the interface of M7C3 carbides and the matrix. The orientation relationships between the secondary phases of the in-situ transforming carbides aged for 13,000 h and 30,000 h at 650 °C were established. The coherent interfaces between these secondary phases became incoherent with prolonged aging treatment due to the exerted strain field of the growing carbides.

A novel medium manganese (MMn) steel with additions of Cr (18%), Ni (5%), V (1%), and N (0.3%) was developed in order to provide an enhanced corrosion resistance along with a superior strength–ductility balance. The laboratory melted ingots were hot rolled, cold rolled, and finally annealed at 1000 °C for 3 min. The recrystallized single-phase austenitic microstructure consisted of ultrafine grains (~1.3 µm) with a substantial amount of Cr- and V-based precipitates in a bimodal particle size distribution (100–400 nm and <20 nm). The properties of the newly developed austenitic MMn steel X20CrNiMnVN18-5-10 were compared with the standard austenitic stainless steel X5CrNi18-8 and with the austenitic twinning-induced plasticity (TWIP) steel X60MnAl17-1. With a total elongation of 45%, the MMn steel showed an increase in yield strength by 300 MPa and in tensile strength by 150 MPa in comparison to both benchmark steels. No deformation twins were observed even after fracture for the MMn steel, which emphasizes the role of the grain size and precipitation-induced change in the austenite stability in controlling the deformation mechanism. The potentio-dynamic polarization measurements in 5% NaCl revealed a very low current density value of 7.2 × 10−4 mA/cm2 compared to that of TWIP steel X60MnAl17-1 of 8.2 × 10−3 mA/cm2, but it was relatively higher than that of stainless steel X5CrNi18-8 of 2.0 × 10−4 mA/cm2. This work demonstrates that the enhanced mechanical properties of the developed MMn steel are tailored by maintaining an ultrafine grain microstructure with a significant amount of nanoprecipitates, while the high corrosion resistance in 5% NaCl solution is attributed to the high Cr and N contents as well as to the ultrafine grain size.

The delayed cracking behavior of a meta-stable austenitic stainless steel AISI 301 under bending condition has been investigated at different temperatures, hydrogen contents and external holding forces. The results reveal that the investigated material with an initial hydrogen content of 1 ppm has good bendability at the temperature range between -20 degrees C and room temperature, which is not susceptible to delayed cracking in atmospheric condition. When the material is pre-charged with 50 ppm hydrogen, the material still shows good bendability. However, it is susceptible to delayed cracking under an external holding force during interrupted bending test. By the measurement of martensitic transformation, the simulation of the stress/strain distributions in the bending specimens and the characterization of fracture surfaces, the effects of hydrogen, stress state and external holding force on delayed cracking behavior have been assessed.

In-situ electrochemical nanoindentation was applied to study the effect of hydrogen on the mechanical properties of Fe-22Mn-0.6C TWIP steel at nanoscale. Distinctive behaviors in three defined grain orientations: (001), (101), and (111) were investigated in a sequence of air, hydrogen ingress, and hydrogen egress processes. The obvious pop-in load drop caused by introducing hydrogen was analyzed using the classical dislocation theory in combination with the “Defactant” model, wherein hydrogen-enhanced homogeneous dislocation nucleation through the reduction of dislocation line energy and stacking fault energy were proposed as the reasons. The dependence of pop-in behaviors on crystallographic orientations was also discussed. Tabor relation-based models were applied to analyze the nanohardness increment, which was related to the hydrogen-enhanced lattice friction and the hydrogen-reduced plastic zone size. The different recovery behaviors of pop-in load and nanohardness during hydrogen egress were assessed according to the different amounts of residual hydrogen in the corresponding affected zone.

The dislocation and twinning evolution behaviors in high manganese steels Fe-22Mn-0.6C and Fe-17Mn-1.5Al-0.6C have been investigated under tensile deformation with and without diffusive hydrogen. The notched tensile tests were interrupted once primary cracks were detected using the applied direct current potential drop measurement. In parallel, the strain distribution in the vicinity of the crack was characterized by digital image correlation using GOM optical system. The microstructure surrounding the crack was investigated by electron backscatter diffraction. Electron channeling contrast imaging was applied to reveal the evolution of dislocations, stacking faults and deformation twins with respect to the developed strain gradient and amount of hydrogen. The results show that the diffusive hydrogen at the level of 26 ppm has a conspicuous effect on initiating stacking faults, twin bundles and activating multiple deformation twinning systems in Fe-22Mn-0.6C. Eventually, the interactions between deformation twins and grain boundaries lead to grain boundary decohesion in this material. In comparison, hydrogen does not obviously affect the microstructure evolution, namely, the twinning thickness and the amount of activated twinning systems in Fe-17Mn-1.5Al-0.6C. The Al-alloyed grade reveals a postponed nucleation of deformation twins, delayed onset of the secondary twinning system and develops finer twinning lamellae in comparison to the Al-free material. These observations explain the improved resistance to hydrogen-induced cracking in Al-alloyed TWIP steels.

A key issue in understanding and effectively managing hydrogen embrittlement in complex alloys is identifying and exploiting the critical role of the various defects involved. A chemo-mechanical model for hydrogen diffusion is developed taking into account stress gradients in the material, as well as microstructural trapping sites such as grain boundaries and dislocations. In particular, the energetic parameters used in this coupled approach are determined from ab initio calculations. Complementary experimental investigations that are presented show that a numerical approach capable of massive scale-bridging up to the macroscale is required. Due to the wide range of length scales accounted for, we apply homogenisation schemes for the hydrogen concentration to reach simulation dimensions comparable to metallurgical process scales. Via a representative volume element approach, an ab initio based scale bridging description of dislocation-induced hydrogen aggregation is easily accessible. When we extend the representative volume approach to also include an analytical approximation for the ab initio based description of grain boundaries, we find conceptual limitations that hinder a quantitative comparison to experimental data in the current stage. Based on this understanding, the development of improved strategies for further efficient scale bridging approaches is foreseen.