Search Results (1,267)

The development of biodegradable polymer composites from renewable resources is important for reducing dependence on petroleum-based plastics and improving the sustainability of short-life-cycle products. However, poly(butylene succinate) (PBS)/poly(lactic acid) (PLA) blends are generally immiscible, and the reinforcing effect of alkali-treated hemp stem fiber (HSF) on their mechanical, thermal, rheological, morphological, and biodegradation behavior remains insufficiently understood. This study investigates PBS/PLA biocomposites prepared at fixed blend ratios of 90/10 and 80/20 wt.% and reinforced with 5–20 phr alkali-treated HSF. Hemp stem fibers are treated using 5 wt.% NaOH, dried, sieved, and compounded with PBS/PLA blends in an internal mixer at 190 °C and 50 rpm for 15 min, and fabricated by hot compression molding at 190 °C for 13 min. The incorporation of HSF improves composite stiffness, with the highest Young’s modulus of 306 MPa observed for the 80/20/15 composition, representing a 71% increase over neat PBS. The maximum flexural strength reaches 48 MPa for 90/10/20, while the highest flexural modulus reaches 1377 MPa for 80/20/20, representing improvements of 21% and 77%, respectively. In contrast, tensile stress at break and elongation at break generally decrease with HSF incorporation because localized fiber agglomeration, incomplete matrix wetting, and interfacial gaps limit effective stress transfer, particularly at higher HSF loadings. The MFR exhibits composition-dependent, non-monotonic behavior. The addition of PLA initially increases the MFR relative to neat PBS, whereas higher HSF loadings generally reduce the MFR due to restricted polymer chain mobility and increased resistance to melt flow. FT-IR results indicate no strong chemical interactions among PBS, PLA, and HSF, while DSC shows nearly unchanged melting temperatures but composition-dependent changes in PBS crystallinity and crystallization behavior. FESEM confirms a phase-separated PBS/PLA morphology with embedded HSF. Soil burial tests show increased weight loss with higher HSF content and exposure time, confirming enhanced biodegradation. Full article

To produce increasingly efficient tools with optimized geometry, additive manufacturing is a suitable solution. However, tool steels, due to their high amount of carbon and hardening elements, may be unweldable and therefore difficult to produce using additive manufacturing methods that employ melting. W360 is a hot-forming alloy, and, in this study, it was produced through laser powder bed fusion (PBF-LB). The microstructure and mechanical properties were evaluated on as-built netshape PBF-LB samples. Despite the presence of many alloying elements, this alloy was not sensitive to cracks, and very good results from the defect analysis (defect surface density < 0.2%) were achieved. Microstructure and hardness are homogeneous in the sample except in the last layer due to an upskin effect. As-built netshape samples exhibit very promising mechanical properties up to 400 °C, which could be further improved by heat treatments. Full article

The present study investigates the combined influence of manufacturing route and material configuration on the mechanical, elastic, viscoelastic, and impact behavior of Kevlar–carbon hybrid laminates. Three eight-ply laminate configurations (V1, V2, and V3) were manufactured through distinct technological routes: fully prepreg-based hot pressing, Kevlar-prepreg/dry-carbon hand lay-up followed by vacuum curing, and multi-stage hybrid consolidation combining repeated hot pressing with subsequent vacuum curing. The experimental characterization included tensile tests according to ASTM D3039, compression tests according to ASTM D695, determination of Young’s modulus from extensometer measurements and Poisson’s ratio using strain-gauge instrumentation, dynamic mechanical analysis (DMA), and low-velocity impact tests under controlled energy conditions. The novelty of this work consists in the integrated process–configuration–property comparison of these Kevlar–carbon hybrid routes within the same experimental framework, rather than in a generic demonstration that manufacturing affects composite laminates. The V1 laminate exhibited the highest strength-related performance, reaching an average tensile strength of 335.88 MPa and a compressive strength of 165.85 MPa, and it also showed the highest DMA storage modulus at 30 °C, E’ = 53.42 GPa. The V2 laminate presented lower tensile performance but the most pronounced damping response, with the highest tanδ peak value. The Young’s modulus determined from the extensometer measurements was 29.26 ± 1.45 GPa for V1, 26.10 ± 0.22 GPa for V2, and 29.52 ± 1.27 GPa for V3, indicating comparable longitudinal stiffness for the V1 and V3 laminates. The results indicate that the measured behavior is governed by the combined effects of reinforcement form, matrix/resin arrangement, consolidation route, and laminate architecture. Direct quantification of laminate compaction, fiber volume fraction, and void content was outside the scope of the present experimental campaign and is identified as a necessary step for future validation. Full article

Direct hot press forming (DHPF) of Zn-coated press-hardening steel (PHS) has not been widely adopted by industry due to liquid metal embrittlement (LME), which occurs when coated steel is hot stamped above the Fe-Zn peritectic temperature (~782 °C). In the present study, low-temperature hot stamping was performed on a 2.0 wt% Mn PHS to avoid LME by preventing liquid zinc formation during plastic deformation while achieving target mechanical properties (yield strength (YS) ≥ 1100 MPa and ultimate tensile strength (UTS) ≥ 1500 MPa) and preserving corrosion performance. The enhanced hardenability, indicated by a critical cooling rate (CCR) of 10 °C/s, enabled a predominantly martensitic microstructure following DHPF at 550–700 °C. Tensile testing of samples extracted from U-shaped panels yielded similar results for uncoated and Zn-coated samples, with a YS of ~1170 MPa, a UTS of ~1600 MPa, a uniform elongation (UE) of 0.05, and a total elongation (TE) of 0.09, demonstrating the preservation of baseline mechanical properties in the coated samples. Microstructural analysis confirmed the absence of LME-induced substrate cracking. Additionally, XRD, SEM-BSE, and EDS analyses confirmed Γ-Fe₃Zn₁₀ formation in DHPF galvanized coatings, with volume fractions averaging ~0.6, well above the critical value of 0.15, irrespective of the DHPF temperature, demonstrating the formation of a cathodically protective coating microstructure. Full article

Corn husk is widely available as an agricultural by-product, yet its use in higher-value composite materials is still limited. This study examined how corn husk mass fraction affects the performance balance of corn husk/poly(lactic acid) (PLA) biocomposites (CHB) intended for moderate-load furniture board components. CHB containing 10 wt% and 30 wt% corn husk was prepared by hot pressing at 200 °C, 10 MPa, and 5 min. Density, water absorption, tensile, compressive, and flexural strength, Shore D hardness, and screw withdrawal resistance were evaluated. Increasing corn husk content from 10 wt% to 30 wt% reduced tensile strength, Shore D hardness, and screw withdrawal resistance. However, flexural strength increased from 22.8 ± 0.5 to 39.8 ± 1.1 MPa, while density decreased from 1.30 ± 0.03 to 1.09 ± 0.05 g/cm³. By contrast, 10 wt% CHB showed higher Shore D hardness and screw withdrawal resistance, reaching 84.1 ± 1.4 and 528.9 ± 22.9 N, respectively. The results indicate that 30 wt% CHB is more suitable for lightweight board components where flexural load-bearing is prioritized, whereas 10 wt% CHB is preferable for parts requiring higher surface hardness and screw connection reliability. Full article

The paper presents a critical review of the key work published to date on the hot ductility of steels in relation to the problem of cracking during continuous casting, including recent publications in the field. Laboratory testing methods that are most appropriate for evaluating cracking susceptibility are examined, with particular emphasis on the hot tensile test. The discussion covers both conventional carbon–manganese (C–Mn) and high-strength low-alloy (HSLA) steels, as well as the more complex advanced high-strength steels. Special attention is given to the influence of strain rate and the role of ferrite, both transformation-induced and deformation-induced, in controlling ductility. Increasing the strain rate invariably improves the ductility of steels containing a thin film of ferrite when it is present. This improvement is attributed to the work hardening of the ferrite, which promotes a more uniform distribution of strain, rather than localisation within the thin ferrite layer, thereby reducing the likelihood of fracture. The difficulties in increasing the strain rate in continuous casters are cited. Finally, based on insights from tensile testing, the paper considers practical approaches to preventing cracking in conventional curved-mould and vertical-mould arc continuous casting machines. Newly designed chamfered moulds have also recently been introduced, and these are claimed to reduce the incidence of corner cracking; their role is also discussed. Full article

Fiber Bragg grating (FBG)-based sensors are increasingly used for temperature and strain monitoring in both fission and fusion facilities, whereas their long-term mechanical reliability under intense γ–neutron fields remains insufficiently understood. Although radiation-resistant FBGs and optical fibers have demonstrated tolerance to fast-neutron fluences approaching 10²⁰ n/cm², the post-irradiation behavior of complete sensor assemblies, including their metallic packaging and joining regions, has received much less attention. This work presents methodology and results of assessing the post-irradiation mechanical properties of packaged FBG-based temperature and strain sensors. The investigated sensors were based on Cu-coated FBGs embedded in 316L stainless-steel bodies and joined using STEMET-1101 brazing filler metal. The sensors were irradiated in the cores of the IVG.1M and WWR-K research reactors to fast-neutron fluences of 4.5 × 10¹⁷ and 1.8 × 10²⁰ n/cm², with absorbed γ-doses of 29.1 MGy and 2.3 GGy, respectively. After decay storage and hot-cell disassembly, tensile testing, microhardness measurements, and SEM–EDS analysis were performed. The results demonstrate that the investigated metal-packaged FBG sensor of this design retained mechanical integrity under high-fluence reactor irradiation. Full article

To meet the combined requirements of high strength, intrinsic corrosion protection, and cost effectiveness for bridge cable wires, 316L/SWRH82B stainless-steel/high-carbon-steel clad wire rods were manufactured under industrial hot rolling conditions. Three initial rolling temperatures of 1000, 1024, and 1047 °C were investigated through metallographic observation, quantitative image analysis, EPMA characterization, SEM fractography, and tensile testing, with 15 specimens tested for each temperature group. The EPMA results, together with the metallographic observations, were used to evaluate carbon diffusion, interfacial elemental redistribution, and decarburization. As the initial rolling temperature increased from 1000 to 1024 and 1047 °C, the decarburized-layer thickness on the SWRH82B side increased from 7.42 ± 1.28 µm to 11.31 ± 1.74 µm and 18.15 ± 1.76 µm, respectively, whereas the carburization-affected-zone thickness on the 316L side increased from 48.36 ± 2.73 µm to 63.04 ± 3.06 µm and 68.73 ± 3.65 µm, respectively, demonstrating pronounced asymmetric interfacial reaction–diffusion. The average tensile strengths of the three groups were 1120.07, 1146.27, and 1152.28 MPa, with corresponding standard deviations of 14.83, 4.55, and 13.34 MPa and coefficients of variation of 1.32%, 0.40%, and 1.16%, respectively. Among the tested conditions, the 1024 °C group exhibited the lowest tensile-strength standard deviation and coefficient of variation, indicating the best tensile stability and mechanical consistency. Although the 1047 °C group achieved the highest average tensile strength, it also exhibited reduced cladding thickness uniformity and renewed mechanical scatter. All 45 tensile specimens were fractured on the SWRH82B side without obvious macroscopic interfacial delamination, indicating that the interface was not the preferential macroscopic fracture path under the present uniaxial tensile-loading condition. However, the intrinsic interfacial bonding strength was not directly quantified in this work. Therefore, 1024 °C is identified as the preferred initial rolling temperature for the specific billet geometry and industrial rolling conditions examined in this work, rather than a universally applicable value. The present study is limited to as-hot-rolled clad wire rods; corrosion performance, multi-pass cold drawability, and the final performance of bridge cable wires after drawing remain to be experimentally validated. Full article

The development of fully biodegradable poly(3-hydroxybutyrate) (PHB)-based materials with improved mechanical performance remains a major challenge due to the limited ductility and processability of this highly crystalline polymer. Blending and plasticisation are viable strategies to enhance PHB toughness; however, the interactions governing polymer–plasticiser compatibility and their impact on structure–property relationships remain not fully understood. In this work, the compatibility and plasticisation mechanisms of two citrate-based plasticisers, tributyl citrate (TBC) and acetyl tributyl citrate (ATBC), were systematically investigated in biodegradable blends based on PHB, polylactic acid (PLA), and poly(butylene adipate-co-terephthalate) (PBAT). Polymer–plasticiser affinity was evaluated through Hansen Solubility Parameters and interaction radius, which indicated good compatibility of PHB with both plasticisers and a stronger affinity for ATBC. Differential scanning calorimetry showed that citrate plasticisers reduced the glass transition temperature, modified crystallisation kinetics, and altered the crystalline morphology of the blends. Dynamic mechanical analysis confirmed the reduction in the glass transition temperature of PHB–PLA systems, which is in agreement with the DSC results. Migration experiments showed equilibrium after approximately 72 h, with PHB–PLA blends exhibiting better plasticiser retention than PHB–PBAT systems. TBC consistently showed higher migration than ATBC, in line with its lower molecular weight and higher volatility. Mechanical testing demonstrated that plasticisation efficiency strongly depended on blend composition: TBC was more effective in enhancing ductility in PHB–PLA blends, whereas ATBC performed better in PHB–PBAT systems. It was also highlighted that the plasticisers had a remarkable ability to substantially increase the ductility of the blends compared with their unplasticised counterparts, as reflected by the pronounced decrease in stiffness and the marked increase in elongation at break. SEM analysis of tensile fracture surfaces evidenced a brittle failure mode for PHB–PLA blends, whereas PHB–PBAT systems exhibited a ductile fracture mode with fibrillar features and clear signs of phase separation. Finally, thermogravimetric analysis showed no appreciable thermal degradation within the processing temperature window used for mixing and hot pressing, confirming the thermal stability of the materials under the selected conditions. These findings establish clear correlations between thermodynamic compatibility, migration behaviour, thermal properties, fracture mechanisms, and mechanical performance, providing useful guidelines for the design of citrate-plasticised PHB-based biodegradable materials. Full article

Hot-water bottles are widely used domestic heat sources, but seam and neck failures can cause scald injuries, and quantitative evidence supporting replacement guidance remains limited. This study compared the tensile behaviour of unused, dry-stored hot-water bottles manufactured in 2022 and 2024, focusing on vulcanised rubber and plasticised PVC constructions. ISO 37 Type 1 dumb-bell specimens were excised from body panels and seam regions and tested in uniaxial tension at 23 ± 2 °C and 50 ± 5% RH using a grip-separation rate of 500 mm min⁻¹. Stress–strain curves were analysed to determine maximum stress, failure strain, toughness and tangent modulus, with seam and face specimens compared within each material year cohort. PVC specimens were consistently stiffer and stronger than rubber specimens but failed at lower strain. Manufacturing year-associated differences were material-dependent: PVC-2022 generally showed higher maximum stress and toughness than PVC-2024, whereas Rubber-2022 underperformed Rubber-2024 at large strain. Seam–face ordering also depended on material and year, with PVC faces outperforming seams, while rubber showed cohort-specific behaviour. These findings indicate that hot-water bottle durability is influenced by both material system and joint region, supporting the need to consider seam performance alongside bulk material properties in safety assessment and replacement guidance. Full article

This study examines the effects of 2 wt% orotic acid (OA) nucleation and injection molding conditions on the crystallization behavior and thermo-mechanical performance of polylactic acid (PLA). Differential scanning calorimetry and X-ray diffraction revealed that 2 wt.% OA accelerates crystallization, enabling molded PLA to achieve crystallinity levels as high as 52–53% under low packing pressure and long hold time. Mechanical testing showed that tensile modulus increased with longer hold time, while tensile strength decreased due to constrained relaxation in the skin layer. Flexural strength increased with packing pressure, whereas flexural modulus decreased as the degree of crystallinity decreased under higher pressure conditions. Heat deflection temperature (HDT) showed the greatest sensitivity to processing, rising from 58 °C to 100–131 °C in optimized PLA–OA samples. The highest HDT values occurred under conditions that promoted both high crystallinity and extended lamellar development with strong α-phase formation. These results demonstrate that combining OA nucleation with controlled injection molding enables high-crystallinity, high-HDT PLA without post-annealing, offering a viable route for producing thermally stable PLA components suitable for hot-fill and reheatable food packaging applications. Full article

To reveal the stress–strain response and microstructure evolution of 38MnVS6 non-quenching and non-tempering steel pistons during hot forging, this study combines finite element simulation with experimental validation to investigate the effects of deformation temperature and strain rate on equivalent stress, true stress–true strain curves, and grain evolution. The results show that the deformation resistance of 38MnVS6 steel decreases with increasing temperature and increases with higher strain rates. Under 1000–1050 °C and a strain rate of approximately 1 s⁻¹, the stress distribution in the forging is relatively uniform, and stress concentration is effectively relieved. An Arrhenius-type high-temperature constitutive equation is established based on peak stress data, yielding a deformation activation energy Q of 335.99 kJ·mol⁻¹, which accurately represents the flow stress variation under different hot deformation conditions. Grain evolution simulated using the CAFE model indicates that 50% deformation promotes dynamic recrystallization and refines the grains. Experimental results show that water cooling increases the tensile strength by approximately 35% compared with air cooling, although the plasticity slightly decreases. In contrast to existing studies on general operating conditions, this paper establishes a coupled correlation mechanism linking the thermal deformation parameters–cooling regime–microstructure–mechanical properties. The findings provide important theoretical foundations and engineering references for the optimization of precision forging processes for non-quenched and tempered steels, the precise control of the microstructure and properties, and the quality control of forgings. Full article

Micro-structured SAE H13 tool steel inserts for polymer injection molding require accurate replication of sub-millimeter features while retaining adequate densification and heat-treatment response. This study compared two powder-based routes on the same hemispherical insert containing pyramidal features of approximately 0.145 mm base width: hot embossing (HE) of water-atomized SAE H13 powder (supplier d50 = 5.7 µm, irregular morphology) compounded with a commercial M1 binder, and material extrusion (MEX) of a commercial gas-atomized SAE H13 filament processed on a Markforged Metal X. Rheological screening selected a 57:43 vol% powder-to-binder ratio for the in-house HE feedstock, and DSC/TGA measurements defined two-step debinding windows. The best HE conditions were 220 °C, 8 MPa, and 45 min for the in-house mixture, and 210 °C, 8 MPa, and 30 min for the granulated commercial filament; the latter showed a 0.15% linear deviation from the silicone replica diameter among the best-rated samples. Under the tested commercial MEX configuration, the pyramidal features were not resolved because the 0.40 mm deposition line width exceeded the target feature base width, causing the slicer to omit the sub-line-width geometry. The defect populations differed qualitatively: HE specimens showed porosity and local cracking associated with powder morphology and pressureless sintering, whereas MEX specimens showed build-direction-aligned inter-raster voids associated with the toolpath. Microhardness and tensile data are therefore interpreted as process-history-specific results rather than as a direct route ranking, because sintering conditions were not uniform across all specimens. The study defines an experimentally bound process-selection limit for SAE H13 micro-tooling: HE remains preferable for sub-nozzle surface features, whereas MEX remains attractive for macro-scale geometric freedom, if resolution, densification, and post-sintering consolidation are addressed. Full article

Steel bridge deck pavements in coastal hot–humid regions are often exposed to the combined effects of moisture, salt, and temperature, which can accelerate material deterioration and shorten service life. To clarify the durability behavior of typical paving materials under such conditions, a comparative study was conducted on three asphalt mixtures used for steel bridge deck pavements: epoxy asphalt mixture (EA-10), dense-graded asphalt mixture (AC-13), and stone mastic asphalt mixture (SMA-10). The mixtures were subjected to hygrothermal salt-water cycling using a mixed chloride-sulfate solution, and their durability was evaluated through air void content, indirect tensile strength, and four-point bending fatigue tests. The results showed varying degrees of deterioration. The air void content of AC-13 increased by about 41.4% after 28 d at 60 °C, suggesting greater susceptibility to internal void damage under severe conditioning. The indirect tensile strength also decreased with wet–dry cycling; at 60 °C and 28 d, the strength retention of EA-10 remained 76.9%, higher than those of AC-13 and SMA-10. After conditioning at 60 °C, the fitted slope of fatigue life for SMA-10 reached −0.0052, compared with −0.0044 for AC-13 and 0.0027 for EA-10, indicating that SMA-10 was the most sensitive to hygrothermal salt attack, whereas EA-10 was the least affected. Overall, the resistance to hygrothermal salt-water damage followed the order EA-10 > AC-13 > SMA-10. The findings help clarify the durability behavior of steel bridge deck paving materials in coastal environments and provide support for durability-oriented material selection. Full article

Mg–Y–Zn alloys have attracted considerable attention for lightweight structural applications; however, the influence of extrusion temperature on microstructural evolution and the underlying mechanisms governing strength–ductility synergy remains insufficiently understood. In this study, a novel YZG921 (Mg–9Y–1.8Zn–1.2Gd–0.5Zr–0.3Ca, wt.%) alloy was fabricated by hot extrusion at temperatures ranging from 480 to 520 °C. The microstructure, mechanical properties, and deformation behavior were systematically investigated using SEM, TEM, EBSD, in situ EBSD, and slip-trace analysis. The results show that extrusion temperature significantly affects the evolution of secondary phases, grain size, and texture intensity. At 500 °C, an 18R-LPSO phase was formed, accompanied by a more homogeneous distribution of secondary phases and the finest grain structure (~3.8 μm), whereas the average grain size remained close to 10 μm for the alloys extruded at 480 °C and 520 °C. Meanwhile, the maximum basal texture intensity decreased from 4.16 to 4.79 m.r.d. to 2.18–2.58 m.r.d. Mechanical testing revealed that the alloy extruded at 500 °C exhibited the optimum strength–ductility balance, with an ultimate tensile strength of 498.4 MPa and an elongation of 13.8%. In situ EBSD analysis showed that the fraction of low-angle grain boundaries increased from ~7% to 43% during tensile deformation, while the average KAM value increased from ~0.5° to 0.88°. Slip-trace analysis further demonstrated that plastic deformation was predominantly governed by basal slip, accounting for approximately 84.2% of the activated slip systems. The superior mechanical performance achieved at 500 °C is attributed to the synergistic effects of grain refinement, LPSO and second-phase strengthening, texture weakening, and sustained strain hardening. These findings provide insights into microstructure–property relationships and offer guidance for the optimization of thermomechanical processing parameters in Mg–Y–Zn alloys. Full article