Search Results (166)

This study examined the value of Sentence Repetition (SRep) tasks as an ecologically valid tool for assessing bilingual children’s morphosyntactic competence. Seventy Greek–Turkish bilinguals and Greek monolinguals (aged 8–12) completed tasks assessing expressive vocabulary, morphological awareness, and SRep. Monolinguals significantly outperformed bilinguals across all tasks, with near-ceiling scores in grammaticality in SRep tasks reflecting earlier acquisition of core Greek structures. In contrast, bilinguals’ performance was significantly lower and varied across conditions: while scores were relatively higher on simple SVO, coordination, and wh-clauses, difficulties emerged in clitic left dislocation, complement clauses, and adverbial clauses—domains of greatest typological divergence between Greek and Turkish. Importantly, SRep performance on grammaticality did not vary with age, despite strong age effects on vocabulary and morphology, suggesting that SRep tasks indexes morphosyntactic knowledge rather than general maturational growth. Regression analyses showed that monolinguals’ SRep performance was best predicted by morphological awareness, whereas bilinguals relied more heavily on expressive vocabulary, reflecting their reduced exposure to Greek and reliance on lexical resources. These findings confirm the fairness and sensitivity of SRep for bilingual assessment, while highlighting the interplay of typological differences and input in shaping bilingual children’s morphosyntactic abilities. Full article

This study examines the impact of rolling direction on Barkhausen noise emission from the low-alloyed steel MC 500 during a uniaxial tensile test. The samples of gauged shape were cut along both the rolling and transverse directions to investigate the process of magnetic anisotropy alterations, as expressed in terms of Barkhausen noise and the extracted features. Barkhausen noise was studied as a function of both elastic and plastic straining (up to plastic strain 21.5%), and the role of domain wall realignment with respect to the rolling direction, as well as the direction of the tensile load, was analysed. Barkhausen noise emission is linked to both the stress state and the microstructure, and the role of external stressing is contrasted with the residual stress state. Barkhausen noise is measured directly during a tensile test (in situ) as well as after unloading (ex situ). It was found that Barkhausen noise is significantly affected by stress directly during the tensile test (in situ), whereas the contribution of residual stresses is less pronounced. Barkhausen noise measured in situ during the tensile test in the direction of the tensile load is higher (about 1100 mV) compared to the transverse direction (about 500 mV). However, this relationship is reversed for the ex situ measurements, especially for the more developed plastic strains above 15%. The influence of rolling direction on Barkhausen noise is relatively minor, and Barkhausen noise after matrix yielding is primarily affected by increasing dislocation density growing from 3 × 10¹⁵ up to 5 × 10¹⁵ m⁻². Full article

During the extrusion of novel nickel-based powder superalloy bars, the die is subjected to elevated temperatures, high pressures, and severe friction, which readily lead to abrasive wear and thermal-fatigue damage. These failures deteriorate the quality of the extruded products and significantly shorten the service life of the die. Frequent repair and replacement of the tooling ultimately increase the overall manufacturing cost. This study investigates the friction and wear behavior of H13 and 5CrNiMo hot-work tool steels under extreme transient high-temperature conditions by combining finite element simulation with tribological testing. The temperature and stress distributions of the billet and key tooling components during extrusion were analyzed using DEFORM-3D. In addition, pin-on-disk friction and wear tests were conducted at 1000 °C to examine the friction coefficient, wear morphology, and subsurface grain structural evolution under various loading conditions. The results show that the extrusion die and die holder experience the highest loads and most severe wear during the extrusion process. For 5CrNiMo tool steel, the wear mechanism under low loads is dominated by mild abrasive wear and oxidative wear, whereas increasing the load causes a transition toward adhesive wear and severe oxidative wear. In contrast, H13 tool steel exhibits a transition from abrasive wear to severe oxidative wear. In 5CrNiMo steel, friction-induced recrystallization, grain refinement, and softening lead to the formation of a mechanically mixed layer, which, together with a stable third-body layer, markedly reduces and stabilizes the friction coefficient. H13 steel, however, undergoes surface strain localization and spalling, resulting in persistent fluctuations in the friction coefficient. The toughness and adhesion of the oxide film govern the differences in wear mechanisms between the two steels. Owing to its higher Cr, V, and Mo contents, H13 forms a dense but highly brittle oxide scale dominated by Cr and Fe oxides at 1000 °C. This oxide layer readily cracks and delaminates under frictional shear and thermal cycling. The repeated spalling exposes the fresh surface to further oxidation, accompanied by recurrent adhesion–delamination cycles. Consequently, the subsurface undergoes alternating intense shear and transient load variations, leading to localized dislocation accumulation and cracking, which suppresses the progression of continuous recrystallization. Full article

The nature of dislocation loops significantly influences their evolutionary behavior and, consequently, affects the material properties, particularly under irradiation conditions. Determining the habit plane of a dislocation loop is the key point to examining its nature using the inside–outside method. In the present study, we introduce a novel technique for determining the habit planes of dislocation loops in the transmission electron microscope (TEM). The traditional inside–outside technique requires an edge-on perspective of the dislocation loop for analysis of the habit plane. In contrast, our innovative method for the precise determination of the habit plane delves into the geometric correlations between the dislocation loop and its projections under different crystal zone axes in TEM without being bound by the restrictive requirement of an edge-on view. It also simplifies the procedure of the inside–outside method. Furthermore, we have discussed the advantages and limitations of various methodologies employed to examine the nature of dislocation loops, as well as the techniques for determining their habit planes. Full article

This study examined the effects of laser shock peening (LSP) and LSP without protective coating (LSPwC) on the microstructure and corrosion behavior of 304L stainless steel using cyclic polarization testing. LSP enhanced corrosion resistance under mild sensitization (650 °C; 5 h) by inducing compressive stress and increasing dislocation density, stabilizing the passive film. Limited improvement was observed under severe sensitization (650 °C; 24 h). Deformation-induced martensite detected by XRD was attributed to mechanical polishing, not LSP. In contrast, LSPwC reduced corrosion resistance across all conditions due to Fe-rich surface oxides that impaired passivation. Full article

The microstructure, precipitation behavior, and mechanical properties of an ultrahigh-strength stainless bearing steel after tempering were investigated using multiscale characterization techniques along with tensile and impact testing. Based on the experimental results, strengthening and toughening mechanisms are discussed. The findings indicate that in samples tempered between 450 °C and 540 °C, tensile strength increases while impact toughness decreases. This is primarily attributed to the precipitation of M₆C and M₂C carbides and a reduction in dislocation density. In contrast, after tempering at 580 °C, the formation of increasing amounts of thick film-like reverted austenite along lath and twin boundaries results in a slight decline in tensile strength accompanied by improved elongation. The dominant strengthening mechanism for samples tempered between 450 °C and 500 °C is the synergistic effect of dislocation strengthening and precipitation strengthening. Above 520 °C, precipitation strengthening becomes the primary mechanism. However, the coarsening of acicular or lamellar M₂C carbides during precipitation appears to significantly degrade toughness. Full article

This study systematically investigates the composition–structure–property relationships in electrospark-deposited Cr-Ta coatings (10, 25, and 40 at.%) on CrNi₃MoVA steel for wear resistance applications. Microstructural characterization reveals that the Cr-10Ta coating exhibits a dense microstructure with excellent metallurgical bonding to the substrate, consisting of a reinforcing Cr₂Ta Laves phase and Fe-Cr solid solution. In contrast, higher Ta content (25–40 at.%) results in the formation of brittle Ta oxides and the development of cracks. Mechanical testing indicates that the Cr-10Ta coating exhibits superior hardness (6.35 GPa) and elastic–plastic deformation resistance (H/E = 0.041, H³/E² = 0.0109), outperforming both higher-Ta coatings and the substrate material. Corresponding tribological assessments reveal that the Cr-10Ta coating achieves the lowest friction coefficient (~0.4) along with a minimal wear rate, which can be attributed to its synergistic combination of fine-grained structure, high dislocation density, and Laves phase reinforcement. The findings underscore that precise control over Ta content serves as an effective strategy for optimizing the wear resistance of Cr-Ta coatings through microstructural engineering. Full article

The performance of ultra-high-purity copper sputtering targets is critical for nanoscale integrated circuit fabrication, yet challenges such as dynamic recovery and recrystallization hinder grain refinement and texture control. In the present work, cryogenic deformation was introduced to address these issues. Through electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and mechanical testing, the microstructure, texture, and mechanical properties of 6N ultra-high-purity copper processed by room-temperature rolling (RTR) and cryorolling (CR) were comparatively investigated. Results reveal that RTR deformation is dominated by slip mechanisms; the RTR sample with 90% reduction exhibits obvious dynamic recrystallization (DRX) and forms a bimodal structure dominated by Copper ({112}⟨111⟩) and S ({123}⟨634⟩) textures. In contrast, CR suppresses thermal activation processes, enabling deformation mechanisms suggestive of twinning activity, leading to ultrafine fibrous structures, while shifting texture components toward Brass ({110}⟨112⟩) and S. Compared to RTR-processed samples, CR-processed samples possess superior mechanical performance. The CR sample with 90% reduction exhibits: a microhardness of 164.60 HV, a yield strength of 385.61 MPa, and a tensile strength of 648.02 MPa, which are, respectively, 33.2%, 91.7%, and 84.6% higher than those of RTR counterparts. Williamson–Hall analysis confirms that the CR sample with 90% reduction achieves finer substructure sizes (~133 nm) and higher stored energy (~22 J·mol⁻¹) by suppressing dynamic recovery, providing a robust driving force for subsequent annealing. This work demonstrates that cryorolling optimizes microstructure and texture through twin-dislocation synergy, providing a fundamental basis for the development of advanced sputtering targets. Full article

Aluminum alloys require improved surface performance to satisfy the demands of today’s aerospace, automotive, marine, and structural applications. This paper compares three key surface hardening methods: diffusion-assisted microalloying, thermomechanical deformation-based treatments, and composite/hybrid reinforcing procedures. Diffusion-assisted Zn/Mg enrichment allows for localized precipitation hardening but is limited by the native Al₂O₃ barrier, slow solute mobility, alloy-dependent solubility, and shallow hardened depths. In contrast, thermomechanical techniques such as shot peening, surface mechanical attrition treatment (SMAT), and laser shock peening produce ultrafine/nanocrystalline layers, high dislocation densities, and deep compressive residual stresses, allowing for predictable increases in hardness, fatigue resistance, and corrosion performance. Composite and hybrid reinforcement systems, such as SiC, B₄C, graphene, and graphite-based aluminum matrix composites (AMCs), use load transfer, Orowan looping, interfacial strengthening, and solid lubrication effects to enhance wear resistance and through-thickness strengthening. Comparative evaluations show that, while diffusion-assisted procedures are still labor-intensive and solute-sensitive, thermomechanical treatments are more industrially established and scalable. Composite and hybrid systems provide the best tribological and load-bearing performance but necessitate more sophisticated processing approaches. Recent corrosion studies show that interfacial chemistry, precipitate distribution, and galvanic coupling all have a significant impact on pitting and stress corrosion cracking (SCC). These findings highlight the importance of treating corrosion as a fundamental design variable in all surface hardening techniques. This work uses unified tables and drawings to provide a thorough examination of strengthening mechanisms, corrosion and fatigue behavior, hardening depth, alloy suitability, and industrial feasibility. Future research focuses on overcoming diffusion barriers, establishing next-generation gradient topologies and hybrid processing approaches, improving strength ductility corrosion trade-offs, and utilizing machine-learning-guided alloy design. This research presents the first comprehensive framework for selecting multifunctional aluminum surfaces in demanding aerospace, automotive, and marine applications by seeing composite reinforcements as supplements rather than strict alternatives to diffusion-assisted and thermomechanical approaches. Full article

In this study, the three internal variables model (3IVM) for dislocation density evolution is further developed into the advanced ABC (advABC) model to simulate the thermo-mechanical behavior of high-purity aluminum (5N). In contrast to conventional FEM packages (e.g., ABAQUS, ANSYS), the present physically based ABC framework directly captures the evolution of the underlying dislocation structure, providing a more coherent prediction of flow behavior. The enhanced model extends the classical formulation by incorporating dislocation annihilation mechanisms and introducing the wall volume fraction as an evolving variable. Simulations are performed over a wide temperature range from −196 °C to 500 °C and at three strain rates of 1, 0.1, and 0.01 s⁻¹. To validate the model, both stress–strain flow curves and microstructural observations obtained via Electron Backscatter Diffraction (EBSD) are used. The simulation results show excellent agreement with experimental data, successfully capturing the temperature- and strain-rate-dependence of the flow behavior, as well as the evolution of dislocation substructures. This work demonstrates the capability of the advABC model to describe both macroscopic and microscopic aspects of deformation. It provides a robust framework for predicting material behavior under complex thermo-mechanical conditions. Full article

China Low-Activation Ferrite (CLF-1) steel, renowned for its excellent thermomechanical properties and irradiation resistance, plays a key role in the development of the R&D of the Chinese Helium-Cooled Ceramic Breeding Test Blanket Module. Cold-worked CLF-1 steels were irradiated with sequential dual ion beams of (Fe²⁺ and H⁺), followed by single He⁺ irradiation at 723 K, with a dose rate of 1.09 dpa/h, to explore the complex relationship between cold work, defect evolution, and irradiation hardening. Samples with cold-working deformations of 0%, 10%, and 50% (denoted as CW 0%, CW 10%, and CW 50%, respectively) were examined. The results based on nanoindentation, TEM, and EBSD reveal that moderate cold work (10%) introduces dense dislocations, acting as effective sinks to suppress irradiation-induced defect accumulation and hardening, while excessive cold work (50%) triggers partial recrystallization under relatively long-time multi-beam irradiation, reducing dislocation density, which leads to the comparable hardening with CW 10%. In contrast, non-deformed samples (0% cold work) exhibit severe irradiation hardening (38.46%). He bubbles and dislocation loops follow non-monotonic trends in number density (CW 50% < CW 0% < CW 10%) and size (CW 50% > CW 0% > CW 10%), governed by the interplay of sink efficiency, thermal diffusion, and recrystallization. These findings highlight that a moderate level of cold-working deformation contributes to enhancing the sink strength, thereby offering a viable approach for designing radiation-tolerant RAFM steels. Full article

A molecular dynamics approach was employed to investigate the interaction behavior between tilt-[110] copper grain boundaries (GBs) and dislocations, with particular emphasis on elucidating the role of GB structural unit (SU) types in the mechanisms of dislocation absorption and transmission. The results reveal that singular GBs composed of continuous and uniform B-type or C-type SUs exhibit a pronounced ability to absorb dislocations, whereby incident dislocations are fully absorbed by the GB and prevented from transmitting across it. In contrast, for discrete GBs containing both C SUs and intrinsic stacking fault facets, the dislocation accommodation capacity of the GB is closely related to the number of C SUs within the discrete region. Multiple continuous C SUs can effectively facilitate dislocation absorption and energy dissipation through a synergistic linkage mechanism. This study underscores the critical role of GB SUs in governing GB–dislocation interactions and provides atomic-scale insights into the microstructural regulation mechanisms of GBs during plastic deformation. Full article

Comprehensive studies of hydrogen embrittlement in high-strength austenitic alloys under cryogenic conditions are scarce, leaving the combined effect of hydrogen charging and extreme temperatures largely unexplored. Given the demands of cryogenic applications such as hydrogen storage and transport, understanding material behavior under these conditions is crucial. Here, we present the first systematic study of hydrogen’s effect at liquid helium temperature (4.2 K) on the mechanical properties of precipitation hardened austenitic alloys, specifically the nickel-based Alloy 718 and austenitic stainless steel A286. Both materials were subjected to pressurized hydrogen charging at 473 K followed by slow strain rate tensile testing at room temperature and at 4.2 K. Hydrogen charging caused significant ductility loss at room temperature in both alloys. In contrast, testing at 4.2 K resulted in increased strength and no evidence of hydrogen embrittlement. Notably, materials pre-charged with hydrogen and tested at 4.2 K exhibited higher stress drop amplitudes and increased strain accumulation during serration events, suggesting persistent hydrogen–dislocation interactions and possible enhanced dislocation pinning by obstacles such as Lomer–Cottrell locks. These results indicate that while hydrogen influences plasticity mechanisms at cryogenic temperatures, embrittlement is suppressed, providing new insight into the safe development of austenitic alloys in cryogenic hydrogen environments. Full article

Buildings crossing active faults often suffer severe damage due to fault dislocation during direct-type urban earthquakes. This study employs physical model tests to systematically investigate the dynamic response mechanisms of the integrated “surface rupture zone–overburden–foundation–superstructure” system subjected to bedrock dislocation. A testing apparatus capable of simulating reverse faults with adjustable dip angles (45° and 70°) was developed. Using both sand and clay as representative overburden materials, the experiments simulated the processes of surface rupture evolution, foundation deformation, and structural response under varying fault dislocation magnitudes. Results indicate that the fault rupture pattern is governed by the bedrock dislocation magnitude, soil type, and fault dip angle. The failure process can be categorized into three distinct stages: initial rupture, rupture propagation, and rupture penetration. The severity and progression of structural damage are primarily determined by the building’s location relative to the fault trace. Structures located entirely on the hanging wall exhibited tilting angles that remained below the specified code limit throughout the dislocation process, demonstrating behavior dominated by rigid-body translation. In contrast, buildings crossing the fault exceeded this limit even at low dislocation levels, developing significant tilt and strain concentration due to differential foundation settlement. The most severe damage occurred in high-angle dip sand sites, where the maximum structural tilt reached 5.5°. This research elucidates the phased evolution of seismic damage in straddle-fault structures, providing experimental evidence and theoretical support for the seismic design of buildings in near-fault regions. The principal theoretical and methodological contributions are (1) developing a systematic “fault–soil–structure” testing methodology that reveals the propagation of fault dislocation through the system; (2) clarifying the distinct failure mechanisms between straddle-fault and hanging-wall structures, providing a quantitative basis for targeted seismic design; and (3) quantifying the controlling influence of fault dip angle and soil type combinations on structural damage severity, identifying high-angle dip sand sites as the most critical scenario. Full article

In this study, shot blasting was employed to enhance the wear resistance and impact toughness of SCMnH11 high-manganese steel. The steel was first fabricated via vacuum casting, followed by forging and water-toughening treatment. Subsequently, the steel was cut to the required dimensions using wire electrical discharge machining before the final shot blasting was performed. The influence of shot blasting duration on the microstructure and mechanical properties was investigated. Shot blasting introduced compressive residual stress and dislocations, resulting in the formation of numerous low-angle grain boundaries. As the shot blasting time increased, the surface grains were progressively refined. The surface hardness increased rapidly from an initial value of approximately 250 HV, reaching a maximum of 643 HV. After 60 min of shot blasting, the thickness of the surface hardened layer reached 600 µm; however, the surface hardness exhibited a trend of first increasing and then decreasing. In contrast, the wear resistance showed the opposite trend. Additionally, the dominant surface wear mechanism transitioned from adhesive wear in the heat-treated sample to abrasive wear in the shot-blasted samples. Compared to the heat-treated sample, the impact toughness of the samples subjected to 5 min and 60 min shot blasting was significantly enhanced. Correspondingly, the fracture mechanism shifted from predominantly ductile fracture to a mixed mode of ductile and cleavage fracture. In summary, shot blasting can effectively enhance the wear resistance and impact resistance of SCMnH11 steel. However, the selection of shot blasting duration is critical. Appropriate parameters can balance work hardening, compressive stress, and surface microcracks, thereby enabling the material to achieve an optimal combination of wear resistance and impact resistance. Full article