Search Results (4,494)

With the development of hydrogen pipelines, hydrogen embrittlement has become a critical issue affecting the safe service of pipeline steels. However, the critical hydrogen concentration for the hydrogen-induced ductile-to-brittle transition and its dependence on grain size remain unclear. Molecular dynamics simulations were performed to elucidate the effects of hydrogen concentration and grain size on the hydrogen-induced ductile-to-brittle transition by investigating hydrogen diffusion, dislocation emission, and fracture evolution in polycrystalline α-Fe. The results demonstrate that, with increasing hydrogen concentration, hydrogen atoms preferentially diffuse along grain boundaries and gradually reach segregation saturation, resulting in continuous degradation of mechanical properties. The initial fracture strain of both fine-grained and coarse-grained models decreases by more than 40%, while fracture energy decreases by more than 50%. Crack surface areas increase by factors of 2.48 and 1.86, respectively, indicating greater hydrogen sensitivity of the fine-grained model. At grain-boundary hydrogen concentrations of approximately 7–9%, suppressed grain-boundary dislocation emission triggers the transition from plastic deformation to brittle intergranular fracture, marking the onset of the hydrogen-induced ductile-to-brittle transition. A quantitative relationship between grain size and grain-boundary atom fraction was established to predict the critical hydrogen concentration for this transition. This study reveals the role of hydrogen concentration in regulating dislocation emission and intergranular fracture, providing insights for hydrogen embrittlement assessment and pipeline material design. Full article

Oxide dispersion strengthened (ODS) austenitic steels exhibit superior high-temperature stability and mechanical properties, which are attributed to the strong pinning effect of nano-oxide particles on dislocations and grain boundaries. The microstructure and properties of ODS steels are intrinsically governed by their fabrication techniques. While powder metallurgy (PM) serves as the predominant synthesis route, the fabrication of austenitic ODS steels faces distinct technical challenges compared to their ferritic counterparts, primarily due to issues such as powder sticking to the milling media. Conversely, although traditional melting processes often lead to oxide agglomeration, coarsening, or flotation, which makes it difficult to achieve a uniform dispersion, they remain of significant interest because of their scalability and cost-effectiveness. Furthermore, emerging technologies such as additive manufacturing (AM) have also been employed for the preparation of ODS steels. This review provides a systematic and comprehensive overview of the recent progress in the fabrication technologies of ODS austenitic steels. The scope encompasses a critical analysis of the merits and limitations of techniques including PM, in situ internal oxidation, melting, and AM, alongside an examination of the potential impacts of adding process control agents (PCA) to mitigate powder sticking during mechanical alloying. Additionally, the microstructural characteristics resulting from different processing routes are discussed in detail, followed by a consolidated evaluation of their mechanical properties. Full article

Conventional grain-oriented silicon steel (GO) relies on AlN/MnS-type inhibitors and long purification anneals, which increase alloy design complexity, energy consumption and cost. This study establishes a dislocation-loop-induced secondary recrystallization route in Fe-3 wt.% Si grain-oriented silicon steel produced by twin-roll strip casting with rare-earth Y microalloying. Steels containing 0, 0.05 and 0.1 wt.% Y were cold-rolled to 0.30 mm and subjected to primary and secondary recrystallization annealing. Electron backscatter diffraction (EBSD) reveals that 0.05 wt.% Y promotes {100}-oriented columnar solidification grains and strengthens the surface {111}⟨110⟩/{111}⟨112⟩ γ-fiber after rolling, increasing shear-band density and Goss nucleation sites while refining the primary-recrystallized matrix. Transmission electron microscopy shows abundant, thermally stable <100> dislocation loops (~50–100 nm) in Y-containing steels, rather than the commonly reported 1/2<111> loops. These <100> loops act as effective grain-boundary pinning centers, suppressing normal grain growth and triggering abnormal Goss growth during high-temperature annealing. The 0.05 wt.% Y steel attains a secondary-recrystallization fraction of ~70%, with B₈ = 1.71 T and P_1.7/₅₀ = 2.81 W·kg⁻¹, whereas the Y-free alloy exhibits only normal grain growth and a weak Goss texture; excessive Y (0.1 wt.%) over-suppresses boundary mobility. The strong Y–vacancy affinity rationalizes the formation, thermal stability and potential recyclability of <100> loops, providing an inhibitor-free, energy-efficient pathway for manufacturing high-performance grain-oriented silicon steel. Full article

This study investigates the compound surface modification of 7075 aluminum alloy through the High-Speed Cutting-Solid Projectile Embedded Water Jet (HSC-SPEWJ) method. The research employed SEM, XRD, TEM, and HRTEM techniques to assess how process parameters such as jet pressure, nozzle distance, and nozzle traverse speed influence surface properties, including surface quality, roughness, microhardness, residual stress, and microstructural evolution in the alloy. The results indicate that the surface of the alloy treated with the SPEWJ process primarily exhibits features such as “craters,” microcracks, and micropores, with the lowest surface roughness recorded at 0.6214 μm. The modification leads to the formation of a plastic deformation layer with depths varying between 28 and 78 μm, with the maximum depth of 78 μm achieved at a jet pressure of 15 MPa. This treatment results in an 8.8% increase in the maximum microhardness when compared to the untreated sample. The greatest work-hardened layer observed extended to a depth of 100 μm. Furthermore, the surface residual compressive stress reached −210.37 MPa, with the stress field extending to 356 μm below the surface. The HSC-SPEWJ treatment also facilitated the formation of high-density dislocations and grain refinement in the alloy, while the size of the Precipitate-Free Zone (PFZ) was reduced by 5 to 10 nm relative to the untreated sample. Full article

Molecular dynamics simulations were employed to investigate the effects of cutting speed and cutting depth on the nanocutting behavior of carbon nanotube (CNT)-reinforced Ni composites. The results show that increasing cutting speed from 50 to 200 m/s reduces the average tangential cutting force by approximately 16.5%, while the cutting temperature increases by 26.7% at a cutting distance of 200 Å. Cutting depth produces a stronger influence on subsurface deformation, with deeper cutting accompanied by increased stress localization, structural disorder, and dislocation activity. In contrast, dislocation evolution exhibits a non-monotonic dependence on cutting speed, indicating that thermal and mechanical effects act concurrently under different cutting conditions. Pronounced changes in local deformation and dislocation behavior are also observed near the CNT–matrix region. These results characterize the coupled thermomechanical and defect responses of the selected CNT–Ni system under different nanocutting conditions. Full article

Background/Objectives: Perilunate dislocations (PLDs) and perilunate fracture-dislocations (PLFDs) are uncommon but severe wrist injuries for which the prognostic influence of treatment timing and initial injury severity remains incompletely defined. This prospective study investigated the association between time to definitive surgery and patient-reported functional outcome and explored clinical and radiographic factors potentially influencing recovery. Methods: Thirty consecutive patients with perilunate injuries were screened at a specialized hand surgery referral center between June 2022 and June 2025. Twenty-five patients completing a minimum 12-month follow-up were included. Clinical outcomes included range of motion (ROM), grip strength, Mayo Wrist Score (MWS), and Patient-Rated Wrist Evaluation (PRWE). Radiographic assessment included scapholunate (SL) gap, carpal height ratio, and SL angle. Associations between treatment timing, radiographic variables, and final PRWE were explored using Spearman correlation and sensitivity analyses. Results: Wrist ROM improved significantly throughout the first postoperative year (all p < 0.0001). Median MWS improved from 70 to 80 (p = 0.0004), while PRWE decreased from 25.75 to 10.5 (p = 0.0002). At 1 year, grip strength reached a median 79% of the contralateral side. Longer time to definitive surgery was associated with worse final PRWE (ρ = 0.578, p = 0.012); this association persisted after exclusion of the most delayed case but disappeared when analysis was restricted to patients treated within 7 days (ρ = 0.111, p = 0.706). Greater preoperative SL gap was also associated with worse final PRWE (ρ = 0.517, p = 0.028), whereas final SL gap was not. Final outcomes did not significantly differ among the principal injury patterns. Conclusions: Perilunate injuries showed substantial functional recovery during the first postoperative year. Marked treatment delay and greater initial scapholunate disruption, rather than injury pattern alone, were associated with worse patient-reported outcome. These findings support prompt diagnosis and timely definitive reconstruction and suggest that quantitative measures of initial injury severity may provide prognostic information beyond conventional PLD/PLFD classification. Full article

The Honningsvåg Igneous Complex (Magerøya, N Norway) provides a unique window into the syn-tectonic crystallization and deformation of mafic-ultramafic cumulates within the Caledonian orogenic belt. This study integrates High-Resolution Electron Backscatter Diffraction (EBSD) mapping, Single-Crystal X-ray Diffraction (SC-XRD) analysis and refinement of the crystal structure, and Electron Probe Microanalysis (EPMA) to decipher the microstructural and chemical evolution of plagioharzburgites and troctolites. Our EBSD results reveal intense intra-crystalline plastic deformation in olivine, characterized by well-developed subgrain boundaries and translational deformation lamellae resulting from high-temperature dislocation creep. SC-XRD structural refinements substantiate this behavior, demonstrating that tectonic strain was accommodated by structural distortion restricted to the highly anisotropic M2 octahedral site. In contrast, clinopyroxene and plagioclase exhibit strong chemical and structural disequilibrium relative to the olivine framework (apparent olivine–orthopyroxene $K_D^{Fe-Mg}$ ≈ 1.08 vs. discordant olivine–clinopyroxene pairs), recording late-stage intercumulus crystallization from fractionated residual melts or episodic magma replenishment in an open system. Furthermore, plagioclase documents a continuous poly-rheological transition, shifting from magmatic alignment and dynamic recrystallization within a dense crystal mush to pervasive brittle micro-fracturing during late-stage tectonic exhumation. Finally, uniform crystallographic orientations of post-magmatic serpentine meshes reveal a strict epitaxial growth mechanism onto the parent olivine, proving that regional ductile deformation had entirely ceased prior to low-temperature H₂O–CO₂ hydrothermal fluid influx. These findings underscore the role of the Honningsvåg intrusion as a highly dynamic, open magmatic system evolving within an active orogenic environment, effectively bridging the gap between deep-seated magmatic processes and crustal-level tectonic deformation. Full article

Background and Objectives: Median nerve entrapment following elbow dislocation is a very rare but serious condition in children. We describe four cases of median nerve entrapment, highlight diagnostic challenges, evaluate the impact of delayed treatment, and propose a treatment algorithm. Materials and Methods: A retrospective review of a consecutive case series of four children with median nerve entrapment following elbow dislocation was conducted. Clinical records, imaging, operative findings, and outcomes were reviewed. Results: In all patients, the causative injury was posterolateral elbow dislocation with an associated medial epicondyle fracture. Three patients had delayed diagnosis of their median nerve entrapment (at 10–31 months post-injury) and required nerve resection with sural nerve grafting; none achieved full neurological recovery. One patient underwent early exploration and decompression (at 4 days post-injury) and made a full recovery. Misattribution of neurological symptoms to transient neurapraxia, under-recognition of radiographic signs, and inadequate early advanced imaging contributed to delayed diagnosis and management. Magnetic resonance imaging was the most useful imaging modality for diagnosing median nerve entrapment, though initial reporting missed entrapment in one case. Conclusions: Prompt recognition and early surgical decompression are critical for optimal recovery in paediatric median nerve entrapment after elbow dislocation. Delayed treatment is associated with poor outcomes. We propose a treatment algorithm to guide management and improve outcomes. Full article

Nanotwinned BCC Fe exhibits a high density of grain boundaries, which act as efficient sinks that promote the recombination of irradiation-induced defects; thus, it has the potential to be applied in irradiation environments. Given that the twin thickness of BCC Fe governs the density of grain boundaries, it represents a critical parameter for practical applications. In this study, molecular dynamics simulations were used to investigate the mechanical properties of nanotwinned BCC Fe and to explore the effects of twin thickness on microstructural evolution at the atomic scale under tensile deformation. The simulations were performed at room temperature (300 K) using the parallel MD package LAMMPS. The results indicated that the peak stress (σ_peak) increased with increasing twin thickness, gradually approaching saturation for twin thicknesses ranging from 20 to 44.8 nm. During tension, the atomic fraction with an FCC structure within twin boundary (TB) regions gradually increased with increasing strain before the peak strain (ε_peak) was reached. Once the strain exceeded ε_peak, the atomic fraction with an FCC structure increased sharply to a value approaching its maximum value, accompanied by dislocation nucleation from the TBs, and subsequently decreased sharply to its minimum value, accompanied by an increase in dislocation emission and the formation of a new BCC phase within the twin interiors. The atomic fraction with a BCC structure was calculated in the models before loading, and the atomic fraction with an FCC structure was calculated as the strain approached its maximum value. The analysis indicated that the variations of the BCC and FCC fractions with twin thickness paralleled those of σ_peak and ε_peak with twin thickness, respectively. Full article

SiC/6082 aluminum matrix composites containing 0, 0.3, 0.5, 0.7, 1, 2, and 3 wt.% micron-sized SiC were fabricated by stir casting. Optical microscopy and SEM/EDS were used to examine grain structure and local particle-containing regions, while XRD was used for qualitative phase assessment. The recorded mean grain sizes for 0, 0.3, 0.5, 0.7, 1, 2, and 3 wt.% SiC are 31.279, 29.004, 27.919, 23.579, 23.453, 21.797, and 17.539 μm, respectively. Tensile strength and Vickers hardness increased to their highest measured values at 2 wt.% SiC and then decreased at 3 wt.%. Elongation varied non-monotonically but also reached its highest measured value at 2 wt.% SiC. The 2 wt.% composite reached a tensile strength of 179.2 MPa, a hardness of 76.99 HV, and an elongation at break of 17.12%. The comparative XRD patterns are dominated by fcc Al. Open SiC and Si symbols denote reference positions only; weak SiC and Si reflections cannot be reliably distinguished under the present signal-to-noise level and mixed acquisition conditions. The XRD results therefore do not independently confirm a retained SiC phase or a quantitative phase fraction. Grain refinement and thermal-mismatch dislocations provide plausible strengthening mechanisms, whereas the modeled Orowan and load-transfer terms are small at the micron-scale particle size. The lower properties at 3 wt.% coincide with pore-like features in representative SEM fields, but the separate effects of porosity, clustering, and interface integrity remain unquantified. Full article

The mechanistic basis for overcoming the strength-ductility trade-off in hexagonal close-packed (HCP) metals via cryogenic surface engineering remains unclear, particularly regarding how processing temperature tailors deformation mechanisms in gradient-structured (GS) pure Zr. Here, pure Zr with a gradient structure was fabricated via surface mechanical attrition treatment (SMAT) at room temperature (RT) and liquid nitrogen temperature (LNT) to systematically investigate the influence of processing temperature on the microstructural evolution, mechanical properties, and deformation mechanisms. The GS Zr processed at LNT achieves a superior strength-ductility synergy, with yield strength increased by 23% and uniform elongation maintained at 81%, significantly outperforming both the CG and SMAT-3-RT counterparts. This enhancement is attributed to an optimized volume fraction of gradient layers and a significantly increased density of deformation twins. Microstructural analysis combined with Schmid factor evaluation reveals that the processing temperature determines the twinning mode: the deformation during SMAT at RT is dominated by basal <a> and prismatic <a> dislocation slips together with {10$\overline{1}$2} <10$\overline{1}\overline{1}$> (T1) twinning, whereas that at LNT involves the same slip modes but {11$\overline{2}$2} <11$\overline{2}\overline{3}$> (C1) twinning, confirming the strong temperature dependence of twin variant selection. Furthermore, during subsequent tensile deformation, prismatic slip emerges as the primary deformation mode in both gradient-structured samples, demonstrating a slip-dominated response once the gradient structure has been achieved. This work elucidates the deformation mechanisms of GS Zr during both SMAT processing and tensile testing, providing guidance for tailoring gradient structures in HCP metals. Full article

Gen-IV nuclear systems demand structural materials with superior high-temperature mechanical integrity, corrosion resistance, and irradiation tolerance. Nickel-based alloys, owing to their excellent high-temperature properties, chemical stability, and irradiation resistance, have become leading candidate materials for key components in advanced reactors such as molten salt reactors and very-high-temperature gas-cooled reactors. This review comprehensively surveys typical reactor-grade nickel-based alloys—Hastelloy N/GH3535, Inconel 718, and Inconel 617—covering their in-service behavior, key properties, processing–microstructure relationships, and irradiation damage research. Special attention is given to irradiation-induced microstructural evolution, including point defect generation and migration during cascades, formation of dislocation loops and voids, helium bubble nucleation and growth, precipitation, and phase transformations, as well as their links to macroscopic property degradation (hardening, embrittlement, swelling, and creep). Recent advances in ion-irradiation experiments, microstructural characterization, nanomechanical testing, and computational methods (first-principles and molecular dynamics) are critically discussed. It is shown that irradiation resistance can be significantly enhanced through compositional optimization, grain-boundary and dislocation engineering, oxide-dispersion strengthening, and the design of heterogeneous interfaces. Finally, future research directions are proposed, emphasizing advanced characterization, multiscale modeling, and data-driven approaches for accelerating the development of next-generation irradiation-resistant nickel-based alloys. Full article

Background/Objectives: Developmental dysplasia of the hip (DDH) is a common pediatric musculoskeletal disorder, and the optimal treatment approach remains controversial. This study compared open and closed reduction in terms of acetabular development, avascular necrosis (AVN) of the femoral head, and the need for subsequent pelvic osteotomy. Methods: This retrospective cohort study evaluated 75 patients (95 hips; 48 right, 47 left) treated for DDH at a tertiary referral center. We performed open reduction in 63 hips and closed reduction in 32. We performed arthrography in 50 hips (52.6%) with a positive Ortolani test to assess reduction quality. We assessed acetabular remodeling using the acetabular index (AI) at 6, 12, and 36 months postoperatively. Dislocation severity was graded using the Tönnis classification, and AVN was assessed using the Kalamchi–MacEwen criteria. Statistical analyses included chi-square tests, independent-samples t-tests, one-way ANOVAs, and Pearson correlation tests, with significance set at p < 0.05. Results: The mean age at surgery was 12.83 ± 5.13 months (range: 6–24 months), and the mean follow-up was 37.78 ± 8.07 months (range: 36–60 months). AVN was observed in 7/63 hips (11.1%) after open reduction and in 0/32 hips after closed reduction (two-sided Fisher exact test, p = 0.091). Among the seven AVN-affected hips, four were Kalamchi–MacEwen grade I, two were grade II, and one was grade III; no grade IV case was observed. Secondary pelvic osteotomy was performed in 13/63 hips (20.6%) after open reduction and 2/32 hips (6.3%) after closed reduction. AI improved during follow-up, decreasing from 38.31 ± 4.47° at 6 months to 31.59 ± 4.28° at 12 months and 23.65 ± 6.03° at 36 months. Higher Tönnis grades were associated with higher 36-month AI values (p = 0.018). Older age at surgery correlated positively with AI at 12 months (p = 0.038) and 36 months (p < 0.001). Conclusions: Open reduction was associated with higher rates of AVN and secondary pelvic osteotomy; however, treatment selection was based on reducibility and arthrographic findings, precluding causal interpretation. Older age at treatment and greater dislocation severity were associated with less favorable acetabular remodeling. Arthrography-assisted closed reduction remains a reasonable option when a stable concentric reduction is achievable, although neither method demonstrated clear superiority. Full article

Background: Pediatric horse-related trauma ranges from minor soft-tissue injuries to potentially fatal trauma. Existing studies often focus on hospitalized patients or selected injury patterns, while broader clinical data remain limited. This study aimed to characterize injury mechanisms, patterns, treatment requirements, and outcomes. Methods: This retrospective cohort study included patients younger than 19 years treated at a Level I trauma center between 2002 and 2023. Demographics, injury mechanisms, injury patterns, treatment, hospitalization, and outcomes were analyzed. Results: A total of 593 patients with 650 injury events were included (mean age at first presentation, 13.0 ± 3.8 years; 90.9% female). Falls predominated (69.8%), followed by kicks (15.2%) and bites (4.6%). Contusions were most frequent (38.5%), followed by fractures (24.5%) and head injuries (16.6%). Injury mechanism was significantly associated with injury pattern (p < 0.001; Cramér’s V = 0.43), and age differed across major injury categories (p < 0.001). Hospital admission was required in 17.4% of events and operative treatment in 5.2%. Fractures (aOR, 5.43; p < 0.001) and head injuries (aOR, 8.85; p < 0.001) were independently associated with hospital admission. Follow-up beyond the initial presentation was documented in 236 of 650 events (36.3%). Among the 234 non-fatal events with documented follow-up, 83.3% were free of complaints; these outcome data should be interpreted as conditional on follow-up availability and subject to potential attrition bias. Two of 593 patients (0.3%) died following atlanto-occipital dislocations after falls involving stirrup entrapment and dragging. Conclusions: Pediatric horse-related trauma comprises distinct mechanism-specific injury patterns. Although most injuries were managed without hospitalization or surgery, fractures and head injuries accounted for a disproportionate treatment burden, while rare complex mechanisms resulted in fatal craniocervical trauma. Full article

Water-cooled nuclear reactors are equipped with internal structural elements made of grade 300 steels, which are subject to embrittlement over their operational lifetime. More specifically, typical internal components are simultaneously exposed to neutron irradiation and pressurized water at elevated temperatures, making them susceptible to intergranular crack initiation. Irradiation damage accumulation markedly affects plastic flow spreading, which is further coupled with strain localization effects. Concurrent exposure to the reactor coolant also contributes to grain-boundary configuration changes in terms of local chemical composition and the resulting tolerance to applied loading. Our approach for evaluating the material response integrates multiple physical mechanisms applicable to post-irradiation austenitic steels, including strain localization in the form of defect-depleted channels, dislocation pile-ups, and the loss of grain-boundary strength. The above time-dependent effects are evaluated and rationalized in terms of the evolution of the dimensionless factor «R», which depends on: (i) the applied loading level, (ii) the irradiation defect size and number density, and (iii) the local grain boundary cohesive energy evolution. The model predictions are consistent with an applied intergranular crack initiation stress of about 700 MPa after combined exposure to pressurized water and neutron irradiation up to 3 dpa at 300 °C. Full article