Search Results (494)

The thermal conductivity (λ) of porous rocks as a function of total porosity, grain size, and fluid saturation is measured and modeled by combining high-precision experiments with a Staged Differential Effective Medium (SDEM) modeling framework. A 1-D divided-bar apparatus with computer-controlled guard heaters with an integrated ultrasonic pulse-transmission system was developed to measure the thermal conductivity and P and S-wave velocities simultaneously. Measurements were made on Fontainebleau sandstone cores and quartz sand packs of varying grain size and effective stresses up to 2000 psi. The sample properties were measured in both dry and water-saturated states. The SDEM model performs significantly better at predicting the saturated thermal conductivities in the sand packs. For the sand packs, the thermal conductivity and compressional velocity are the highest and most stress-sensitive for the fine-grained material. In contrast, the shear velocity is largest in the coarse-grained material. The SDEM model is adapted from previous acoustic models for use in understanding thermal conductivity. These joint models accurately reproduce the evolution of both thermal conductivity and bulk modulus during increasing compaction and varying saturation. A single parameter fits both the dry and saturated data, which allows Gassmann-style fluid substitution for the thermal conductivity. This model improves the prediction of in situ thermal conductivity from sonic well logs. Full article

With the strategic shift toward reducing reliance on critical raw materials, Cobalt-free eutectic high-entropy alloys (EHEAs) have emerged as a pivotal frontier for high-performance structural applications. This review systematically elucidates the synergistic relationship between Co-free alloy design and the non-equilibrium solidification mechanisms of Selective Laser Melting (SLM). The ultra-high cooling rates (10⁵–10⁸ K/s) inherent in SLM are shown to refine eutectic lamellae to the sub-micron scale (typically <300 nm), effectively suppressing the macro-segregation common in conventional casting. We evaluate the design principles of Al-Cr-Fe-Ni and related systems, noting that SLM-processed Co-free EHEAs frequently achieve yield strengths exceeding 1000 MPa and ultimate tensile strengths (UTSs) surpassing 1300 MPa, while maintaining tensile elongations above 10%—a significant improvement over the coarse-grained structures produced by traditional methods. Furthermore, the study identifies critical processing windows, such as laser energy densities (60–120 J/mm³), required to mitigate micro-cracking and achieve near-full density (>99.5%). By synthesizing recent experimental breakthroughs and AI-driven modeling, this review provides a quantitative roadmap for the precision manufacturing of cost-effective, high-performance EHEAs, bridging the gap between theoretical alloy design and industrial additive manufacturing. Full article

The demanding operational requirements of ultra-deep oil and gas exploration present formidable challenges for material performance, necessitating the development of novel cemented carbides that combine high strength-toughness with exceptional corrosion resistance. In this study, Cr₂(C,N) was employed as a grain inhibitor to introduce N into the dual-scale structured WC-Co cemented carbide system for the fabrication of novel cemented carbides. The effects of Cr₂(C,N) addition on the microstructural organization, mechanical properties and corrosion resistance behavior were systematically investigated. The experimental results show that the addition of Cr₂(C,N) effectively prevents the direct contact of these coarse WC grains and allows more fine WC grains to be retained to fill the regions between these coarse WC grains and the Co binder phase, thereby suppressing Co pool formation and resulting in a continuous and uniform Co binder network. When the addition amount of Cr₂(C,N) reaches 0.6 wt.%, the dual-scale structured cemented carbide achieves the optimal comprehensive mechanical properties, with a transverse rupture strength of 3182.3 MPa, a fracture toughness of 18.68 MPa·m^1/2, and a hardness of 1140.4 HV₃₀. Meanwhile, the optimization of microstructure, the formation of a passive film, and the stabilization of the fcc-Co phase jointly contribute to the superior corrosion resistance of this composition. Full article

The conservation of tuff- and coral rock-built architectural heritage structures (AHS) is challenging because access to original tuff and coral rock has become difficult and severely limited due to urbanization, land reclamation, the depletion of stone quarries, anti-mining and anti-quarrying legislation. An emerging approach to address this issue is to create compatible “replacement” rocks via geopolymerization, a process that is more sustainable and greener than the use of conventional cement and concrete. To explore the potential of geopolymers for AHS conservation strategies, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were implemented; 103 eligible articles were identified and classified into geopolymers for AHS (34 articles), tuff-built AHS (60 articles), and coral rock-built AHS (9 articles). Tuff substrates in AHSs appear in a variety of colors (yellowish-brown, grayish-cream, reddish-brown, pale greenish-gray and pink hues), densities (1.0–2.5 g/m³), and compressive strengths (3–100 MPa). Meanwhile, coral rock substrates in AHSs appear in whitish-cream color and are coarse-pored (1–5 MPa), fine-grained (8–15 MPa), and calcarenite (50–60 MPa). In terms of geopolymer formulation, metakaolin was reported as the most popular main precursor or admixture, while NaOH and Na₂SiO₃ were used simultaneously as alkaline activators. Aggregates used in geopolymer formulations depended on local availability, including quartz sand, river sand, crushed stones, carbonate stones, volcanic rock, volcanic sand, tuff, brick, ceramic tiles, and waste materials. Aesthetics, chemical composition, physical attributes, and mechanical properties have been identified as key criteria to ensure geopolymer compatibility for AHS conservation application. To date, geopolymers have been applied for AHS conservation as repair mortars, consolidants (i.e., grout and adhesives), and masonry strengthening (i.e., fiber-reinforced mortar). Finally, geopolymers formulated for AHS conservation have similar durability as the original substrate based on accelerated aging tests (i.e., salt mist, wet-dry, and freeze–thaw) and long-term outdoor exposure experiments. Full article

Molecular engineering has traditionally followed a structure–function paradigm based on well-defined, folded architectures. However, intrinsically disordered proteins and regions (IDPs/IDRs) reveal that nature also exploits disorder as a functional design strategy. Here, we argue that intrinsic disorder can be understood as a biomimetic design principle for molecular and materials engineering. From a soft matter perspective, IDRs function through statistical ensembles, weak multivalent interactions, and collective behavior rather than fixed structure, with sequence features encoding a molecular grammar that governs phase behavior, viscoelasticity, and responsiveness. These principles closely parallel those found in associative polymers and colloidal systems. Recent advances in coarse-grained modeling, machine learning, and inverse design further enable disorder to be treated as a controllable engineering variable. By reframing intrinsic disorder as a programmable and bioinspired design strategy, this Perspective highlights its potential for the development of adaptive and responsive biomimetic materials. Full article

Nanostructured metallic materials are widely applied in various fields due to their excellent comprehensive properties. Enhancing mechanical properties through microstructure design has emerged as a novel strengthening strategy. In this contribution, the microscopic mechanical behavior of coarse-grained and gradient-structured nanocrystalline NiCoAl alloys during tensile deformation was investigated via molecular dynamics simulations. Based on the investigation of compositional effects, the Ni₆₀Co₃₀Al₁₀ alloy composition was selected, exhibiting a yield strength of 4.92 GPa. The results indicate that increasing Al content reduces the material’s strength, Young’s modulus, and work hardening effect. Furthermore, by introducing a gradient structure with grain sizes gradually varying from 1.8 nm to 6.5 nm into the alloy, the yield strength reaches 1.8 GPa and the flow stress reaches 3.35 GPa, demonstrating a significant improvement compared to the uniform coarse-grained structure. Upon introducing the gradient structure into the alloy, it was observed that geometrically necessary dislocations (GNDs) nucleate in the coarse-grained region during deformation and gradually extend towards the fine-grained region. The increased grain boundary density effectively impedes dislocation motion and enhances dislocation pinning capability, thereby inducing continuous strain hardening and improving plasticity. By promoting the accumulation and interaction of grain boundary dislocations, the gradient structure achieves further strengthening and strain hardening in the alloy, providing a theoretical basis and simulation foundation for designing high-performance advanced alloys. Full article

Aimed at improving the mechanical performance of welded joints in stainless steel composite materials, this research investigates the evolutionary characteristics of microstructure at the interface between the transition layer weld and base layer weld through electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) analytical techniques. In addition, molecular dynamics simulation methods are employed to conduct an in-depth study on the atomic diffusion behavior during the welding process. The results show that carbon and chromium atoms undergo asymmetric diffusion at the interface, forming a decarburized and a carburized zone. The diffusion coefficient of carbon atoms was the largest, with the diffusion mechanism being interstitial diffusion. Followed by chromium atoms, the diffusion coefficient of Fe was the smallest. On the base layer weld side, two structural zones with different grain sizes were formed; the zone close to the interface was a coarse ferrite microstructure with the lower geometrically necessary dislocation density, the zone far from the interface was a finer-grained ferrite and pearlite microstructure. As the welding heat input of the transition layer weld increases, the average density of geometrically necessary dislocations, the decarburized layer thickness, the average grain size, and the diffusion coefficients of Cr and C atoms at the interface all exhibit a concomitant upward trend. Concurrently, a carbon–chromium compound precipitates at the interface. Full article

The solid structure of industrial sinter comprises seven mineral associations (A, B, C, D, Ds, E, N) which have different relative abundances of key minerals, textures and spatial relationships to micro-macropores and hematite nuclei. Among the key characteristics of the mineral associations: (MA), MA-A comprises abundant SFCA-I microplates with hematite; MA-B consists of disseminated fine-grained magnetite in a network of SFCA-III microplates; MA-C is similar to MA-B but contains patches of dendritic SFCA-III with larnite and minor glass; MA-D comprises magnetite surrounded by coarse prisms of SFCA within glass; MA-Ds, a subtype of MA-D, includes SFCA with secondary skeletal hematite; MA-E consists of anhedral to skeletal magnetite or hematite in a matrix of glass; and MA-N comprises unmelted hematite nuclei from iron ore feedstock. SFCA-III and SFCA-I are dominant in MA-B and MA-A, respectively, whilst magnetite is the most common mineral in MA-C, MA-D/Ds and MA-E. Low-temperature sintering samples are largely of MA-A to MA-D (62 area %), which contain higher combined levels of SFCA-SFCA-III and lower levels of magnetite-dominant MA-E (12.6 area %), whereas high-temperature/magnetite sintering examples had high levels of magnetite-dominant MA-E (31.6 area %) and MA-D/Ds (52.1 area %) and low levels of MA-A to MA-C (8.9 area %). It is proposed that the formation of each MA is controlled by the peak sintering temperature attained, the dwell time at higher temperature which adversely allows fractional crystallisation to tie up more Fe in magnetite rather than forming SFCA phases during cooling, and especially a slower rate of cooling which promotes the formation of more SFCA family phases at lower temperatures. However, local variations in chemistry inherited from raw material granulation and assimilation during sintering of Si-rich gangue or ore nuclei are also important. Full article

Sliding bearing alloy layers must combine excellent tribological performance with reliable metallurgical bonding, but conventional fabrication methods often suffer from coarse grains, chemical segregation and poor interface adhesion. Annular coaxial laser wire-feed cladding, by providing more uniform heat input and rapid solidification, is expected to mitigate these deficiencies; however, systematic studies of this technique applied to tin-based Babbitt alloy layers remain limited. In this work, Babbitt layers produced by conventional casting and by annular coaxial laser wire-feed cladding were compared in terms of microstructure, phase constitution, hardness and tribological behavior. The results indicate that laser cladding can produce continuous, dense and well-bonded coatings and markedly refine the SnSb phase, reducing grain size from approximately 100 μm in the cast material to 10-20 μm. Hardness increased from 25.3 HB to 27.6 HB, while tribological performance improved substantially: the coefficient of friction decreased by about 38.19% and the wear volume was reduced by approximately 10.46%. These improvements are attributed mainly to the rapid solidification, low dilution and more uniform phase distribution associated with annular coaxial laser cladding, demonstrating the strong potential of this process for fabricating high-performance tin-based Babbitt bearing layers. Full article

In the present contribution, Hot-rolled and annealed ferritic stainless steel T4003 with three distinct Mo contents (0%, 0.1%, and 0.2%) served as the research subject. Weldability tests were implemented by means of gas metal arc welding. Coupled with microstructural characterization, mechanical property assessments, and electrochemical corrosion tests, the regulatory mechanism of Mo on the microstructure and properties of the HAZ was systematically elucidated. Results demonstrate that the influence of Mo content on the evolution of the coarse-grained region structure of heat affected zone becomes significant. The addition of 0.1% Mo refines the grains, increasing the fraction of lath martensite to 70–75% while limiting the maximum width of the coarse-grained zone to 0.64 mm. Meantime, the addition promotes the precipitation of (Nb, Ti, Mo) (C, N) composite carbonitrides, enhancing overall performance through synergistic grain refinement and second-phase strengthening. The sample with 0.1% Mo exhibits an average low-temperature impact energy of 16.3 J at −40 °C, with the highest Vickers hardness in the HAZ, favorable strength–plasticity synergy of the welded joint, and optimal corrosion resistance. The coarse-grained zone of the 0.2% Mo sample is dominated by coarse δ-ferrite and features a larger width, and the HAZ shows inferior mechanical properties and corrosion resistance. The precipitated phases in the 0.2% Mo segregate along the grain boundaries and distribute in a chain-like distribution, exacerbating the deterioration of material properties. These findings provide a technical reference for optimizing the composition design of T4003 ferritic stainless steel and ensuring its safe application in railway freight vehicles. Full article

Tightness of homogeneous embankment dams is often ensured by means of upstream water barriers, such as bituminous concrete facings, concrete slabs, shotcrete membranes, metallic sheets, geomembranes, and cement blankets. The stability analysis of these dams, especially in areas with high seismicity, must include the hydraulic and mechanical effects resulting from an extensive, sudden cracking of the impervious facing. To this purpose, in this paper, simple, original analytical solutions are proposed to estimate the position of the exit point on the downstream slope of the dam, the maximum height of the saturation front at the downstream face, and the time required for the saturation front to reach the downstream face. These variables generally depend on several factors, such as the geometry of the dam, homogeneity or heterogeneity, the permeability coefficient of the dam body materials, and resistance laws to describe the seepage flow. The high number of these factors requires the development of advanced 2D/3D FEM analyses, often computationally heavy and complex to implement. Although approximate, the proposed solutions may however allow us to define the role of the various factors and their interaction, to quickly deduce the main, preliminary design indications. Full article

Coarse-grained soil is a commonly used filling material in foundation engineering, and its static shear characteristics are significantly affected by the initial stress state. For coarse-grained soils, clearly defining the drainage conditions and improving the accuracy of pore water pressure measurements are crucial in static shear tests. Based on GDS dynamic and static true triaxial equipment, this paper systematically conducts static shear tests on coarse-grained soil under three-dimensional initial isotropic, three-dimensional initial anisotropic, and plane strain states. The effects of initial mean principal stress, initial generalized shear stress, initial intermediate principal stress coefficient, and water content on the stress–strain relationship, strength, modulus, and friction angle of coarse-grained soil are analyzed. The research shows that under the same initial mean principal stress, the peak strength under a plane strain state is the largest, and that under a three-dimensional initial anisotropic state is the smallest. The peak strength of coarse-grained soil with optimal water content is generally higher than that under a saturated state; under a three-dimensional initial anisotropic state, the peak strength decreases with an increase in the initial generalized shear stress and increases with an increase in the initial intermediate principal stress coefficient. The research results provide a theoretical basis for the analysis of mechanical behavior of coarse-grained soil in foundation engineering. Full article

The typical microstructure and mechanical properties of twin-roll cast (TRC) 2139 aluminum alloy were investigated and compared with mold casting (MC) 2139 alloy. This work pioneers the application of TRC to produce 2139 Al-Cu-Mg alloy, a material that is challenging for rapid solidification. The TRC process resulted in a denser dendritic structure, with the composition of intermetallic compounds, primarily Al₂Cu and Al₂CuMg, remaining largely stable throughout the casting process. After solution treatment, the recrystallized grains in the MC sheets were uniformly distributed, while the TRC sheets exhibited a more localized and refined recrystallized microstructure, particularly within coarse second-phase regions. Following heat treatments, the TRC sheets showed a significant increase in the Ω phase after T6, with a slight growth in size and a uniform distribution, while the Ω phase in T8 showed an increased density and smaller size, which diffused evenly across the material. The TRC process uniquely refines the microstructure and enhances Ω phase precipitation, yielding a 10%+ improvement in strength and ductility over conventional casting. The mechanical properties of the TRC sheets improved significantly: tensile and yield strengths increased by over 10% after T6, compared to MC sheets, with elongation slightly higher in TRC. T8 treatment further enhanced the mechanical properties of the TRC sheets, achieving an improvement in strength with only a minor trade-off in elongation. This establishes TRC as a superior industrial route for high-performance aluminum sheets, offering a promising industrial route, delivering substantial improvements in both strength and ductility over conventional casting methods. Full article

Torrential flows are hazardous hydro-geomorphological phenomena characterized by sudden water discharge and intense sediment transport. They occur in mountainous areas where hydrometeorological monitoring is often limited or absent. The lack of such data hinders the identification of flow types and sediment transport conditions, reducing the effectiveness of mitigation measures. To address this issue, the current study focuses on geomorphic characteristics of torrential watersheds and identifies indirect indicators of torrential activity. The sedimentological and geomorphic signatures of torrential flows in the lower Damdere River catchment (Eastern Rhodopes Mountains, southern Bulgaria) were characterized. To capture inter-annual variability in torrential activity and differences between the Damdere and its tributary the Duandere, we sampled riverbed deposits. We also sampled areas upstream and downstream of the check dam to assess its influence. Samples were analyzed for grain size distribution, petrography, and mineralogy (X-ray diffraction). Results show contrasting controls on sediment supply and transport: the Duandere delivers relatively coarse material, whereas the Damdere attains higher transport capacity during torrential events. The check dam is largely infilled and exerts only local effects by trapping finer sediments upstream. Downstream, the channel retains its torrential character. Inter-annual comparison upstream of the structure shows sediment fining linked to lower flows. Petrographic and XRD data point to mechanically driven erosion and rapid sediment transfer. The results underline the importance of geological–geomorphological indicators in the lack of long-term monitoring in similar mountain catchments and can support flood risk management. Full article

This study investigates the development of sustainable PVC-based composites filled with surface-modified wood flour for potential use in modern, energy-efficient building systems. The aim was to enhance the mechanical performance, thermal stability, and interfacial compatibility of PVC plastisols by incorporating fine- and coarse-grained coniferous wood flour modified with silane and surfactants. Composites were formulated using emulsion PVC (Vinnolit E-2059), bis(2-ethylhexyl) adipate as a plasticizer, and MARK-17 MOK as a thermal stabilizer, and were gelled under pressure at 150 °C. Their physical, mechanical, structural, and thermal characteristics were evaluated using density and hardness measurements, SEM, thermomechanical analysis, DMA, and TGA. The results demonstrated that composites containing fine-grained, silane-treated wood flour (Lignocel C-120) exhibited the most advantageous balance of stiffness, elasticity, and thermal resistance, attributable to improved polymer–wood interfacial adhesion. The findings confirm the potential of modified wood flour as an effective bio-based filler enabling the design of durable, thermally stable coating and insulating materials with reduced environmental impact. The proposed composites may serve as protective, bonding, or insulating layers in sustainable construction, supporting the development of innovative, wood-based materials for low-carbon building applications. Full article