Journal of Materials Science最新文献

This study investigates the effects of thermal aging on the crystallographic texture, dislocation density, and tensile behavior of a novel high entropy alloy (HEA) with the composition Al₂Fe₅₃Ni₃₅Cu₅Ti₅ (at.%). Using a combination of X-ray diffraction (XRD) and high-resolution electron backscatter diffraction (HR-EBSD), three different heat-treated configurations (ConFig 1: water-quenched; ConFig 2: aged 3 h at 530 °C; ConFig 3: aged 10 h at 530 °C) were characterized to correlate microstructural evolution with mechanical performance. The alloy displayed a primarily FCC structure across all treatments, with progressive formation of Ni₃Ti (HCP) and AlNi₃ (L1₂) precipitates during aging. Lattice distortion, initially severe in the as-cast state, reduced significantly with aging, as reflected in the transition toward near-cubic symmetry. Dislocation density followed a nonlinear trend, decreasing in ConFig. 2 due to recovery but rising in ConFig. 3 with the formation of a secondary phase. Texture analysis revealed a dominant {001} < 100 > component in early stages, shifting toward a pronounced Goss ({110} < 001 >) orientation with prolonged aging. Correspondingly, tensile testing showed an increasing yield and ultimate tensile strength from 250/334 MPa in ConFig 1 to  400 MPa/465 MPa in ConFig 3, accompanied by a drop in elongation from 55% to 28%. These findings highlight the critical role of precipitation and texture evolution in tuning the strength–ductility balance of HEAs through controlled thermal processing.

High nitrogen steel (HNS) is an advanced engineering material characterized by an exceptional combination of high strength, high toughness, excellent corrosion resistance, low magnetism, and good biocompatibility. These superior properties make it particularly suitable for demanding applications in critical fields such as marine engineering, nuclear energy equipment, medical implants, and national defense systems. Based on the latest international research progress, this paper systematically reviews the status and technical characteristics of mainstream joining technologies for HNS, including the fusion welding, friction stir welding (FSW), and brazing. The study focuses on key aspects of HNS welding, such as the shielding gas atmosphere, heat input control, welding filler material selection, and critical parameter optimization. Furthermore, it conducts an in-depth analysis of the process control mechanisms and their effectiveness in existing welding methods for HNS, identifies shortcomings in current research on HNS joining systems, and outlines future prospects. The primary objective of this paper is to consolidate current knowledge and provide a reliable reference and theoretical foundation for advancing research and industrial applications in the field of HNS welding.

A novel thermomechanical process is proposed, wherein intercritical warm rolling followed by varying cold rolling reductions is conducted prior to the identical annealing. The study investigates the resulting microstructural characteristics and their influence on the tensile behavior of δ-ferrite-containing medium-Mn steel. The alteration of cold rolling reductions from 0 to 60% results in significant microstructural variation in annealed samples, abbreviated as CRA0, CRA40, and CRA60. For instance, the combination of lath and equiaxed ferrite (α)-austenite (γ) microstructures in the CRA0 sample transforms to a more homogeneous structure with primarily equiaxed morphology. The δ-ferrite phase, on the other hand, remains as equiaxed morphology but shows a significant reduction in average grain size with cold rolling deformations. The overall recrystallization and elemental partitioning during annealing are attributed to these variations. Furthermore, the process yields the tensile strength > 800 MPa and ductility ranging from ~ 30 to ~ 58% without the presence of a yield point plateau, which is typically observed in cold-rolled samples. The observed tensile properties are mainly ascribed to the TRIP effect and HDI strengthening mechanisms operating during deformation. Variations in austenite stability lead to differences in the TRIP effect, while associated strain partitioning during deformation leads to different interface-affected zones and hence varying HDI strengthening. These combined factors govern the observed strength–ductility balance in the samples. In addition, phase-wise bulk texture analysis reveals a strong correlation with the TRIP effect and highlights the role of ferrite (α/δ) during tensile deformation.

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Instantaneous monitoring of human motion is prominent for advancing healthcare and human–machine interaction. However, fabricating flexible strain sensors that integrate high sensitivity, broad detection range, and biodegradability via a one-step process remains challenging. Here, we propose a one-step wet electrospinning strategy to develop a biodegradable sensor using poly(L-lactide-co-ε-caprolactone) (PLCL) and multi-walled carbon nanotubes (MWCNTs). By directly electrospinning PLCL into an MWCNT-loaded coagulation bath, the MWCNTs are uniformly anchored onto fiber surfaces through electrostatic and van der Waals interactions, eliminating the need for post-treatments. This simplified process enables: Ultrahigh sensitivity (gauge factor = 968.8) and exceptional stretchability (ε > 800% strain), Robust durability (> 5000 cycles) with a low detection limit (0.08%), controllable biodegradability via PLCL/MWCNT composite design. The sensor precisely detects diverse motions, from subtle throat vibrations to large joint bending angles (30°–90°), demonstrating its potential for wearable health monitoring and intelligent robotics. Importantly, this work provides a low-cost, scalable fabrication paradigm for high-performance flexible electronics, while addressing environmental concerns through material degradability.

Polycarbosilane (PCS) is an ideal precursor for polymer-derived silicon carbide (SiC), which is an important engineering ceramic material with excellent thermal and mechanical properties. Nevertheless, facile preparation of high molecular weight PCS precursors with excellent processability remains a challenging task in both industrial and academic sectors. In this study, low molecular weight PCS is covalently linked with coupling agent containing alkenyl groups using hydrosilylation reaction, resulting in significant improvement on the PCS molecular weight. For instance, compared to the original PCS with a molecular weight of 1297 g/mol (M_n), the modified PCS shows a M_n as high as 3441 g/mol under optimized reaction conditions, suggesting that the molecular weight of the product increases up to almost three times. Moreover, the thermal decomposition temperature and ceramic yield of the product increases to 450 °C and 81.3%, comparing to those of 350 °C and 67% of unmodified PCS. This hydrosilylation can be conducted under mild reaction conditions, offering advantages over other methods that require high pressure or high temperature. The resulting products not only exhibit a desirable increase in ceramic yield but also contain vinyl or allyl groups on polymer chains that can be applicable for further functionalization of the ceramic precursors.

Graphical abstract

Hydrogels, which are three-dimensional crosslinked hydrophilic polymer networks capable of retaining over 90% water content, have garnered significant attention in flexible sensor technologies due to their unique combination of intrinsic flexibility, biocompatibility, and tissue-adhesive properties This study proposed a strategy to tailor the mechanical properties and electrical conductivity of protein hydrogels by immersing them in ammonium sulfate solutions, thereby modulating protein chain aggregation via the Hofmeister effect. The characteristics of the hydrogel, including their chemical structure, microstructure, thermal stability, swelling performance, mechanical properties and conductivity and strain-sensitivity performance, were investigated to assess the effects of ammonium sulfate on the egg white hydrogel and evaluate the potential application in the field of wearable sensing technology. Results demonstrate that ammonium sulfate affected hydrogen bonding and the secondary structure of protein chains, leading to protein aggregation and a denser three-dimensional network microstructure. The Hofmeister effect endowed the hydrogels with exceptional thermal stability, excellent freezing resistance (< − 20 °C), and remarkable swelling resistance. The compressive fracture strength of the ammonium sulfate-immersed hydrogels were improved to 5.0 times and 8.8 times that of the original egg white protein hydrogels, respectively. Also, the electrical conductivity reached 4.93 S/m. The ammonium sulfate-immersed hydrogels exhibited stable and sensitive electrical signal transmission performance, which could accurately monitor the movement of many joints in the human body as strain sensors. Thus, we developed a facile single-step salt-assisted immersion strategy to fabricate mechanically robust, naturally derived protein-based hydrogels with great potential for motion detection and information recording.

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The development of high-performance flame-retardant epoxy (EP) composites is critical for improving fire safety in practical applications. In this study, a DOPO-derived flame retardant (DD) was selected as a flame retardant to enhance the flame retardancy of EP. Considering the potential roles of metal centers in catalyzing char formation and oxidative reactions, a bimetallic Zn/Co-ZIF was innovatively synthesized in this study. Furthermore, its morphology was tuned to a two-dimensional (2D) sheet-like structure through a controlled synthesis strategy to better exert gas-phase barrier effects during combustion. The results revealed that EP/10DD/2D Zn/Co-ZIF composite achieved a 30.4 and 18.9% reduction in peak heat release rate (pHRR) and total heat release (THR), respectively, and attained a V-0 rating in the UL-94 test. Additionally, the average CO yield and total smoke production were markedly decreased, indicating improved smoke suppression. Additionally, 2D Zn/Co-ZIF enhanced the mechanical performance of EP composites, SEM and interfacial analysis revealed that 2D Zn/Co-ZIF promoted strong interactions with the EP matrix and DD, improving dispersion and compatibility. This work demonstrates a promising strategy for creating multifunctional flame retardants by combining phosphorus-based compounds with 2D metal–organic frameworks (MOFs), enhancing both flame retardancy and mechanical performance in EP composites.

Selective Laser Melting (SLM) has emerged as a powerful technique for manufacturing Ti-6Al-4V components, widely adopted in biomedical, aerospace, and other high-performance industries. Despite its advantages, the SLM process is challenged by a multitude of interdependent parameters, making it difficult to consistently produce components with optimal tensile strength (TS) and hardness. Moreover, the high cost, time consumption, and expertise required further complicate the process. To address these issues and to enhance prediction performance, this study presents a novel machine learning (ML) approach enhanced by Limited-memory Broyden–Fletcher–Goldfarb–Shanno with Box constraints (L-BFGS-B) optimization to improve prediction accuracy and predict the TS of Ti-6Al-4V parts fabricated through SLM. Among five optimized ML models tested, ensemble models (Random Forest (RF) and Gradient Boosting (GB)) showed the highest performance, with the GB model achieving < 10 MPa mean absolute error (MAE), less than 1% of predicted strength. Experimental fabrication with optimized parameters resulted in a favourable distribution of fine grain structures and controlled volume fractions of α, α′ (martensitic), and minor amount of β phases, all resulting from the higher cooling rate of SLM. Microstructural and mechanical characterization revealed that improvement in TS and hardness of SLMed samples compared to conventionally made is due to the predominant finer α′ martensite structure generated by the rapid melting and solidification of SLM process. These findings highlight the effectiveness of the optimization strategy in enhancing model accuracy and robustness, especially within ensemble learning frameworks.

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This study investigated the hot deformation behavior of the Cu–9Ni–6Sn–0.6Cr alloy under different deformation conditions through isothermal hot compression experiments. The alloy was tested under four different strain rates (1 s⁻¹, 0.1 s⁻¹, 0.01 s⁻¹, and 0.001 s⁻¹) and four deformation temperatures (750 °C, 800 °C, 850 °C, and 900 °C). The microstructural evolution of the alloy was analyzed, and its constitutive model and hot processing map were developed based on the peak stress. The results show that the alloy exhibits a hot deformation activation energy of 227.754 kJ/mol. The material demonstrates a strain hardening index of 8.0408, with a strong correlation (R² = 0.96065) observed between empirical measurements and theoretical predictions. The constructed hot processing map reveals that the alloy exhibits optimal formability under specific thermomechanical conditions, particularly within the 830–885 °C temperature range and at strain rates of 0.001–0.005 s⁻¹.

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Lithium-sulfur (Li-S) batteries hold considerable promise as a next-generation energy storage technology, exhibiting high theoretical specific energy and capacity. However, their commercialization is hindered by challenges such as the shuttle effect of lithium polysulfides (LiPSs) and slow redox kinetics. In this study, nickel-iron layered double hydroxides (NiFe-LDHs) with varying Ni:Fe ratios are synthesized and utilized as interlayers for Li-S batteries. Among the samples, the NiFe-LDH-3 (Ni:Fe = 3:1) interlayer demonstrated the optimal performance. Li-S batteries with NiFe-LDH-3 interlayer demonstrated an initial capacity of 1469 mAh g⁻¹ at 0.1 C. The reversible capacity is recorded at 424 mAh g⁻¹ after 400 cycles at 0.5 C. The low capacity decay rate is determined to be 0.147% per cycle. The superior performance can be attributed to the NiFe-LDH-3 interlayer’s capacity for chemical adsorption of LiPSs, physical obstruction of LiPSs migration via its layered configuration, facilitation of Li⁺ transport, and catalyzation of LiPSs conversion through the redox activity of Ni and Fe ions. Consequently, this effectively inhibits the shuttle effect and accelerates reaction kinetics. This work demonstrates that NiFe-LDHs interlayers are effective in enhancing the performance of Li-S batteries.