Search Results (2,042)

This study investigates the effects of B₄C content (2.5, 5, 7.5, and 10 wt.%) on the microstructure and wear resistance of laser cladding 316 stainless steel coatings on a 2Cr12MoV steel substrate. The coating was prepared by laser cladding technology. The phase composition, microstructure evolution, microhardness, and tribological properties of the coating were analyzed. The results show that the decomposition of B₄C particles is complete, and the phase composition of the coating includes Austenite, Fe₂₃ (B₃C₃), Cr₂₃ (B_1.5C_4.5), and a Fe-Ni solid solution. The increase in B₄C content significantly increased the microhardness of the material from 206 HV_0.2 (substrate) to 829 HV_0.2 (10 wt.% B₄C) by 4.02 times. Wear resistance also improved, with the 10 wt.% coating exhibiting the lowest wear rate (10 × 10⁻⁸mm³/N·m) due to fine-grained and dispersion strengthening mechanisms. However, excessive B₄C (10 wt.%) induced cracks from increased brittleness, resulting in higher friction coefficients. The wear mechanism consists of fatigue wear, adhesive wear, and oxidative wear, and the degree of wear decreases with the increase in B₄C content. This work demonstrates that the addition of B₄C effectively improves the hardness and wear resistance of 316 stainless steel coatings, providing practical insights into surface engineering in high wear applications. Full article

Cu matrix composites, because of their high mechanical strength, are often used as conductors in high-performance electrical applications. These composites are manufactured through thermomechanical processing, which introduces a high density of particles that act as obstacles to dislocation motion. Increasing the density of these particles enhances the mechanical strength of the conductors, which we tested under static loading. Under cyclic loading, especially pulsed electrical mechanical loading, conductors may soften, harden, or even fail. Failure is likely to occur whenever the applied stress exceeds the flow stress of the conductors. Understanding and predicting the performance of conductors under cyclic loading can help researchers estimate the lifespan of any apparatus made from these conductors. The performance of conductors depends on whether the strengthening particles are characterized by ionic interatomic bonding or metallic bonding. During fabrication, we observed both the accumulation of dislocations and the dissolution of particles (which added more solute atoms to the matrix). Because both dislocations and solute atoms tend to migrate at room temperature or higher, the complexity of microstructure changes increases in composites under cyclic loading. To minimize such complexity, we designed our test to determine fatigue properties at 77 K. We subjected the conductors to cyclic fatigue tests using a load-controlled mode (the mode most commonly used in applications). This work sheds light on the correlation between tensile properties and fatigue properties in our composite conductors. We found that the correlation varied, depending on whether the conductors had been strengthened by ionic bond or metallic bond particles. Full article

Induction quenching is critical for high-strength bulb flat steel, yet the influence of the heating temperature on mechanical property uniformity across sections remains underexplored. This study systematically investigates the effect of the induction heating temperature on mechanical property uniformity, prior austenite grain size, and microstructural evolution in bulb flat steel. Experimental results reveal that increasing the induction heating temperature from 845 °C to 1045 °C induces distinct mechanical responses: the yield strength disparity between the bulb and flat sections decreases by 93% (from 94 MPa), significantly improving sectional uniformity. Microstructural analysis indicates that prior austenite grain size coarsens with higher induction heating temperatures. The quenched microstructure comprises martensite and bainite in the bulb core, while the flat section is entirely martensitic. The yield strength differential between the bulb and flat sections is governed by temperature-dependent strengthening mechanisms: dislocation strengthening dominates at 845 °C~985 °C, with the bulb region exhibiting higher strength due to increased dislocation density, while grain boundary strengthening prevails at 1045 °C, where the flat region benefits from finer grains. Full article

To investigate the microscopic mechanism of aging-induced “dewetting” at the matrix/filler interface in Nitrate Ester Plasticized Polyether (NEPE) propellant, this study decoupled the aging process into two factors: crosslinking density evolution and nitrate ester decomposition. Molecular dynamics (MD) simulations were employed to construct all-component matrix models and matrix/filler interface models with varying aging extents. Key parameters including crosslinking density, mechanical properties, free volume fraction, diffusion coefficients of the matrix, as well as interfacial binding energy and radial distribution function (RDF) were calculated to analyze the effects of both aging factors on “debonding”. The results indicate the following: 1. Increased crosslinking density enhances matrix rigidity, suppresses molecular mobility, and causes interfacial binding energy to initially rise then decline, peaking at 40% crosslinking degree. 2. Progressive nitrate ester decomposition expands free volume within the matrix, improves binder system mobility, and weakens nitrate ester-induced interfacial damage, thereby strengthening hydrogen bonding and van der Waals interactions at the interface. 3. The addition of a small amount of bonding agent improved the interfacial bonding energy but did not change the trend of the bonding energy with aging. Full article

This study analyzes the effect of artificial aging on the mechanical deformational and optical properties of various paper samples, which allows us to evaluate their durability and suitability for long-term storage. The methods of accelerated aging, measuring the breaking length, specific resistance, elongation, and fracture strength, were used, and the optical characteristics were estimated by the R₄₅₇ and CIE whiteness indices, as well as opacity. Mechanical measurements (breaking length, specific resistance, elongation, and fracture strength) revealed that bleaching reduces residual lignin and strengthens interfiber bonds, boosting pine pulp strength by up to 8%. Optical properties initially improve slightly, then increase sharply after the second bleaching cycle and stabilize, while opacity decreases, providing greater light transmittance. After accelerated aging, the following deterioration is observed: for bleached samples, R₄₅₇ whiteness changes; and for unbleached samples, CIE whiteness and opacity increase. After aging, aspen pulps and kraft papers retained over 90% of their initial strength and whiteness, whereas untreated and office papers lost up to 20–25%. These findings identify that aspen-based and kraft papers demonstrate better mechanical deformational and optical properties, which makes it possible to predict the operational characteristics of paper depending on the processing and aging methods used. Full article

Mg alloys are highly attractive for biodegradable surgical clips because of their low density and good biocompatibility; however, their limited strength and ductility restrict their widespread application. To overcome this limitation, this study employed screw rolling (SR) to produce a Mg–3Zn–0.2Ca alloy with a fine microstructure and an average grain size of 1.6 µm. Experimental results showed that the SR process improved the comprehensive tensile properties of the alloy, increasing the yield strength, ultimate tensile strength, and elongation from 192.6, 234.4 MPa, and 21.7% for the pre-extruded alloy to 252.3, 289 MPa, and 39.5%, respectively. Quantitative analysis of the strengthening behaviour identified grain refinement as the primary strengthening mechanism, along with considerable contributions from Orowan and dislocation strengthening. The ultra-high-tensile ductility was primarily attributed to the low internal stress, nano-sized precipitates, texture weakening, and activation of multiple slip systems. These findings provide a strategy for simultaneously increasing the ductility and strength of Mg alloys and lay a foundation for applying them as biodegradable clips. Full article

NiAl coatings are critical for protecting components in high-temperature environments. In order to improve the mechanical properties of NiAl coatings, in this study, the elastic and electronic properties of NiAl coatings alloyed with different contents of rare earth element (REE) Y were investigated by using the density functional theory (DFT). It was found that NiAl alloys with 3.125 at.% of Y exhibited higher hardness, while those with 6.25 at.% of Y showed better ductility. This phenomenon is explained by population analysis, which reveals that the covalency of Ni-Ni and Al-Al bonds is stronger in Ni₁₅YAl₁₆ than in Ni₇YA₈, whereas Ni-Al bonds exhibit stronger covalency in Ni₇YAl₈. Additionally, the ionicity of Y-Al bonds is higher in Ni₇YAl₈ than in Ni₁₅YAl₁₆. These results deepen our understanding of how rare earth elements modify the mechanical properties of NiAl alloys, thereby providing a theoretical basis for further exploration of their strengthening mechanisms. Full article

To expand the fundamental understanding of eutectic high-entropy alloys (EHEAs), three novel alloy systems—Cr_1.3Ni₂TiAl, CoCr_1.5NiTi_1.5Al_0.2, and V_0.3CoCr_1.2NiTi_1.1Al_0.2—were rationally designed through synergistic phase diagram analysis and thermodynamic parameter calculations. Comprehensive microstructural characterization coupled with mechanical property evaluation revealed that these alloys possess FCC+BCC dual-phase architectures with atypical irregular eutectic morphologies. Notably, progressive microstructural evolution was observed, including amplified grain boundary density and the emergence of brittle nanoscale precipitates. Mechanical testing demonstrated superior compressive yield strengths in these alloys compared to conventional FCC+BCC EHEAs with ordered eutectic structures, albeit accompanied by reduced fracture strain. The Cr_1.3Ni₂TiAl alloy exhibited optimal ductility, with a maximum fracture strain of 15.6%, while V_0.3CoCr_1.2NiTi_1.1Al_0.2 achieved peak strength, with a compressive yield strength of 1389.5 MPa. Multiscale analysis suggests that the enhanced mechanical performance arises from the synergistic interplay between irregular eutectic configurations, expanded grain boundary area, and precipitation strengthening mechanisms. Full article

Cu-Fe in situ composites often face challenges in achieving high strength during cold rolling due to the inefficient transformation of partial Fe phases into fibrous structures. To uncover the underlying mechanisms, this study systematically investigates the co-deformation behavior of Cu and Fe phases in a Cu-10Fe alloy subjected to cold rolling at various strains. Through microstructure characterization, texture analysis, and mechanical property evaluation, we reveal that the Cu matrix initially accommodates most applied strain (ε_vm < 1.0), forming shear bands, while Fe phases (dendrites and spherical particles) exhibit negligible deformation. At intermediate strains (1.0 < ε_vm < 4.0), Fe phases begin to deform: dendrites elongate along the rolling direction, and spherical particles evolve into tadpole-like morphologies under localized shear. Concurrently, dynamic recrystallization occurs near Fe phases in the Cu matrix, generating ultrafine grains. Under high strains (ε_vm > 4.0), Fe dendrites progressively transform into filaments, whereas spherical Fe particles develop long-tailed tadpole-like structures. Texture evolution indicates that Cu develops a typical copper-type rolling texture, while Fe forms α/γ-fiber textures, albeit with sluggish texture development in Fe. The low efficiency of Fe fiber formation is attributed to the insufficient strength of the Cu matrix and the elongation resistance of spherical Fe particles. To optimize rolled Cu-Fe in situ composites, we propose strengthening the Cu matrix (via alloying/precipitation) and suppressing spherical Fe phases through solidification control. This work provides critical insights into enhancing Fe fiber formation in rolled Cu-Fe systems for high-performance applications. Full article

The monoculture planting in terraced tea plantations has led to severe soil degradation, which poses a significant threat to the growth of tea plants. However, the mechanisms by which intercropping systems improve soil health through the regulation of soil microbial communities at the micro-topographical scale of terraced tea plantations (i.e., terrace surface, inter-row, and terrace wall) remain unclear. This study investigates the effects of intercropping Ophiopogon japonicus in a five-year tea plantation on the soil physicochemical properties, enzyme activities, and microbial community structure and functions across different micro-topographical features of terraced tea plantations in Wuyi Mountain. The results indicate that intercropping significantly improved the soil organic matter, available nutrients, and redox enzyme activities in the inter-row, terrace surface, and terrace wall, with the effects gradually decreasing with increasing distance from the tea plant rhizosphere. In the intercropping group, tea leaf yield increased by 13.17% (fresh weight) and 19.29% (dry weight) compared to monoculture, and the disease indices of new and old leaves decreased by 40.63% and 38.7%, respectively. Intercropping strengthened the modularity of bacterial networks and the role of stochasticity in shaping bacterial communities in different micro-topographic environments, in contrast to the patterns observed in fungal communities. The importance of microbial phyla such as Proteobacteria and Ascomycota in different micro-topographical features was significantly regulated by intercropping. In different micro-topographical zones of the terraced tea plantation, beneficial bacterial genera such as Sinomonas, Arthrobacter, and Ferruginibacter were significantly enriched, whereas potential fungal pathogens like Nigrospora, Microdochium, and Periconia were markedly suppressed. Functional annotations revealed that nitrogen cycling functions were particularly enhanced in inter-row soils, while carbon cycling functions were more prominent on the terrace surface and wall. This study sheds light on the synergistic regulatory mechanisms between micro-topographical heterogeneity and intercropping systems, offering theoretical support for mitigating soil degradation and optimizing management strategies in terraced tea agroecosystems. Full article

Refractory metal-based Mo-Si-B alloys have long been considered the most promising candidates for replacing nickel-based superalloys in the aerospace and energy sector due to their outstanding mechanical properties and good oxidation of the Mo-silicide phases. In general, the addition of vanadium to Mo-Si-B alloys leads to a significant density reduction, while small amounts of titanium provide additional strengthening without changing the phase evolution within the Mo_ss-Mo₃Si-Mo₅SiB₂ phase field. In this work, high-energy ball milling studies on Mo-40V-9Si-8B, substituting both molybdenum and vanadium with 2 and 5 at. % Ti in all constituents, were performed to evaluate the potential milling parameters and investigate the effects of Ti doping on the milling characteristics and phase formation of these multicomponent alloys. After different milling durations, the powders were analysed with regard to their microstructure, particle size, oxygen concentration and microhardness. After heat treatment, the silicide phases (Mo,V)₃Si and (Mo,V)₅SiB₂ precipitated homogeneously within a (Mo,V) solid solution matrix phase. Thermodynamic phase calculations using the CALPHAD method showed good agreement with the experimental phase compositions after annealing, confirming the stability of the observed microstructure. Full article

In this study, an innovative internal oxidation-powder metallurgy combined process was employed to controllably generate nano-sized Cr₂O₃ reinforcing phases within the Cu matrix. The Cu/Cr₂O₃ composites were successfully fabricated using the hot-press sintering (HP) method, and a systematic comparison was made between the microstructure and mechanical properties of composites prepared by internal oxidation and external addition methods. The results show that internal oxidation primarily occurs during the sintering process rather than ball milling. Compared with external addition, the internal oxidation method effectively prevents particle aggregation and achieves a uniform distribution of Cr₂O₃ particles in the Cu matrix. When the Cr content reaches 5 wt%, the Cu-5%Cr composite exhibits optimal mechanical properties, with a yield strength of 282.7 MPa and ultimate tensile strength of 355 MPa, representing increases of 43% and 34% over pure copper, respectively, while maintaining an elongation of 12.6%. The Cr₂O₃ particles generated via internal oxidation enhance their strength through Orowan strengthening and dislocation pinning, thereby significantly improving mechanical performance without compromising plasticity. This research provides a novel process optimization approach for developing high-performance dispersion-strengthened copper matrix composites. Full article

The interface morphology plays an important role in the mechanical properties of laminated metal composites (LMCs). In this study, binary LMCs with different crystallographic characteristics, namely Fe/Al (BCC/FCC), Ni/Al (FCC/FCC), and Mg/Al (HCP/FCC), were fabricated through the hierarchical roll-bonding process. The influence of interface morphology on the mechanical properties of the binary LMCs was investigated systematically. The results show that the strength–hardness coefficient (R) decreases with increasing interface morphology factor (α) for the LMCs, indicating that the strengthening effect of LMCs decreases with increased curvature of the interface. The experimental results reveal that α increases with the increase in rolling deformation (thickness reduction) for the LMCs, which is consistent with the finite element simulation results. The dependence of mechanical properties on interface morphology is mainly related to the microstructural inhomogeneity caused by localized deformation in the harder layer, including the formation of shear bands and variations in grain morphology, size, and orientation, which can lead to stress concentration in the necking zone. Full article

The extreme environment of aerospace requires severe material properties, and in situ autogenous ZrC–NbC dual-phase reinforced titanium matrix composites have attracted much attention. In this study, TiC/Ti composites (TMC1–TMC4) with different NbC contents (0–9 wt%) were prepared and investigated in depth by various means and ANSYS simulations. The results show that the variation in NbC content significantly changes the TiC morphology from fine needles at 0 wt% to needles with a small amount of ellipsoidal grains at 3 wt%, to an ideal uniform distribution (mostly granular or nearly spherical) at 6 wt%, and to a large number of aggregates (dendritic or coarse rod-like) at 9 wt%. In terms of mechanical properties, the compressive strength and elongation firstly increased and then decreased, and reached the optimum at 6 wt% NbC, with the ultimate compressive strength as high as 1379.50 MPa, the compressive yield strength at 817.3 MPa, the compressive strain up to 38.73%, and typical ductile fracture characteristics; at 9 wt%, it transformed into a mixed fracture mode, with a decrease in performance. ZrC and NbC synergistically stabilize the microstructure, with the best synergistic effect at 6 wt% NbC, which effectively improves the overall performance and meets the requirements of aerospace applications. The simulation is highly compatible with the experiment and verifies the experiment; this helps to reveal the mechanism, provides guidance for the design of high-performance materials, and promotes the development of materials technology in the aerospace field. Full article

Despite the growth of fruit production, the challenge of postharvest fruit loss particularly in tropical and subtropical fruits due to spoilage, decay, and natural deterioration remains a critical issue, impacting the global food supply chain by reducing both the quantity and quality of fruits postharvest. Edible coatings have emerged as a sustainable solution to extending the shelf life of fruits and decreasing postharvest losses. The precise composition and application of these coatings are crucial in determining their effectiveness in preventing microbial growth and preserving the sensory attributes of fruits. Furthermore, the integration of nanotechnology into edible coatings has the potential to enhance their functionalities, including improved barrier properties, the controlled release of active substances, and increased antimicrobial capabilities. Recent advancements highlighting the impact of edible coatings are underscored in this review, showcasing how they help in prolonging shelf life, preserving quality, and minimizing postharvest losses of subtropical fresh fruits worldwide. The utilization of edible coatings presents challenges in terms of production, storage, and large-scale application, all while ensuring consumer acceptance, food safety, nutritional value, and extended shelf life. Edible coatings based on polysaccharides and proteins encounter difficulties due to inadequate water and gas barrier properties, necessitating the incorporation of plasticizers, emulsifiers, and other additives to enhance their mechanical and thermal durability. Moreover, high levels of biopolymers and active components like essential oils and plant extracts could potentially impact the taste of the produce, directly influencing consumer satisfaction. Therefore, ongoing research and innovation in this field show great potential for reducing postharvest losses and strengthening food security. This paper presents a comprehensive overview of the latest advancements in the application of edible coatings and their influence on extending the postharvest longevity of main subtropical fruits, emphasizing the importance of maintaining the quality of fresh and fresh-cut subtropical fruits, prolonging their shelf life, and protecting them from deterioration through innovative techniques. Full article