A Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ high-entropy alloy film was designed as a Cr- and Al-free metallic sensing layer for thin-film strain gauges in high-pressure hydrogen environments. CALPHAD calculations predicted a BCC/B2-type phase field, while XRD, EBSD and GIXRD results supported a BCC-type structure without direct confirmation of long-range B2 ordering. Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ films deposited on Si reference substrates at 150 and 300 W retained broad BCC-type diffraction features. The 300 W film showed a more continuous cross-sectional morphology, good metallic conductivity and a comparable nanomechanical response with slightly higher hardness. Device-level tests were then performed using Cr/AlN/Fe₅Cu₅V₃₀Ti₃₀Nb₃₀ TFSGs on 316L stainless-steel substrates. The devices exhibited average absolute apparent zero shifts of 16.08 με in 12 MPa N₂ and 17.79 με in 12 MPa H₂, with an additional H₂-associated apparent response of only 1.71 με. Static tensile tests in 12 MPa H₂ confirmed a linear strain response with a gauge factor of 1.72 ± 0.01.

Local chemical heterogeneity is a typical feature of selective laser melted (SLM) austenitic stainless steel and is closely related to its hydrogen-assisted deformation behavior. In this work, molecular dynamics simulations are performed to investigate the effects of local segregation on stacking fault energy, hydrogen diffusion, and dislocation motion in austenitic stainless steel. Three representative alloy compositions, Fe₇₁Cr₁₇Ni₁₂, Fe₇₁Cr₂₃Ni₆, and Fe₇₁Cr₁₁Ni₁₈, are used to describe local composition variation associated with segregation in SLM-relevant austenitic stainless steel. The results show that Ni-rich regions exhibit relatively higher stacking fault energy and faster hydrogen diffusion, whereas Cr-rich regions show lower stacking fault energy and reduced hydrogen mobility. Hydrogen further decreases the stacking fault energy in all three alloy models and exerts a stronger influence on local defect energetics than composition variation alone. Shear simulations indicate that elemental segregation itself has only a limited direct effect on dislocation motion, whereas its interaction with hydrogen leads to a more evident retardation of partial dislocation propagation within the segregation region. These findings highlight the coupled roles of local composition variation and hydrogen in governing defect evolution and local deformation behavior in segregation-containing regions.

W-modified TiAlN coatings were developed as hydrogen permeation barrier coatings for magnetic materials. TiAlN and TiAlN-W coatings with comparable thicknesses of approximately 1.5 μm were deposited on Fe and NdFeB substrates by physical vapor deposition. GIXRD and SEM results showed that W modification was associated with a change from weakly crystalline, columnar TiAlN to a more compact, low-crystallinity W-modified Ti–Al–N coating with amorphous/nanocrystalline features inferred from the broad diffraction response. XPS analysis identified low-valence W-related species, such as W–N/Wⁿ⁺-related bonding, together with overlapping Ti 3p/W–O_x contributions and surface oxide/oxynitride species, indicating a modified surface and near-surface chemical environment. Electrochemical hydrogen permeation tests on Fe substrates showed that TiAlN reduced the steady-state current density from 2.54 ± 0.86 to 0.55 ± 0.08 μA cm⁻², corresponding to a permeation reduction factor of 4.68 ± 0.16. In contrast, TiAlN-W showed no obvious hydrogen breakthrough during the 15,000 s test period, and the current density remained below the practical detection limit of 0.01 μA cm⁻², giving a lower-bound permeation reduction factor of >250. In high-pressure H₂ exposure tests, the TiAlN-W-coated NdFeB sample remained macroscopically intact after exposure to 5 MPa H₂ at 23 °C for 24 h, whereas the uncoated and TiAlN-coated samples were pulverized. The markedly improved hydrogen permeation resistance is associated primarily with the more compact cross-sectional morphology and W-modified coating structure.