Improvement Of Mechanical Properties Research Articles

Supertoughened Polylactic Acid/Polybutylene Adipate Terephthalate Blends Compatibilized with Ethylene-Methyl Acrylate-Glycidyl Methacrylate: Morphology and Mechanical Properties by the Response Surface Methodology.

Optimized extrusion melt-blending of polylactic acid (PLA) polymer with a minor biopolymeric phase, polybutylene adipate terephthalate (PBAT), and compatibilized with random ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA-GMA, Trademark: Lotader AX-8900) led to an outstanding improvement in mechanical properties. At the noncompatibilized PLA-PBAT (80-20) blend point, significant enhancement (∼4500%) in toughness and elongation-at-break was already obtained without compromising any elastic properties. The effect of the compatibilizer content on the mechanical properties of the PLA-PBAT (80-20) blend was investigated by an optimal custom response surface methodology. Thus, 2 wt % Lotader content was determined to be optimal by a numerical optimization methodology with a desirability value, D, of 0.882 to maximize toughness and elongation-at-break. The compatibilization and thermal behavior of the Lotader-modified blends were analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Upon adding the compatibilizer, the original phase-separated morphology of the blends changed from PBAT quasi-spherical domains to nearly elongated elliptical ones. It was also found that the interfacial boundary line of the domains faded away, which revealed that interfacial compatibility was achieved. The thermostability of the blends remained largely unaltered following the incorporation of PBAT and Lotader. Moreover, while PBAT exhibited a minor influence on the crystallinity of PLA, Lotader had no discernible impact on crystallinity, as evidenced by the DSC thermograms. Thus, the compatibilizer at the optimal point in the optimized blend ratio led to the formation of a phase-separated morphology that combined internal cavitation, interfacial cavitation, and strong adhesion features at the right proportions in the microstructure which underlies the micromechanisms driving the remarkable enhancement of as much as 7100% in toughness and ductility.

Improvement of Mechanical Properties of β-AlSiFe Phase by Doping Transition Metals (M = Cr, Mn, V, Ti, and Zr): A First-Principles Study

Improvement of Mechanical Properties of β-AlSiFe Phase by Doping Transition Metals (M = Cr, Mn, V, Ti, and Zr): A First-Principles Study

Superstrong and tough silk fibers cross-linked with functionalized graphene

Natural silkworm silks with an intriguing integration of good strength, modulus, toughness and biocompatibility, have been widely used in textile and medical industry. However, the strength of silkworm silks is inferior to that of spider dragline silks, which are the strongest natural silks but extremely low yield. Herein, we develop a feasible strategy to continuously produce superstrong and tough regenerated silk fibers (RSFs) through the reconstruction of hierarchical and cross-linked architectures. Amine functionalized graphene (NH2-G) has been introduced to improve the content of β-sheet and crystalline orientation, and glutaraldehyde (GA) has been used to bridge NH2-G and silk micro/nanofibrils (SNFs) to form a highly interconnected and closely packed network, resulting in the remarkably improvement of mechanical properties. The resultant fibers exhibit an excellent tensile strength of 1029.6 ± 144.8 MPa, a Young's modulus of 16.8 ± 1.5 GPa, and a toughness of 277.4 ± 17.0 MJ/m3, exceeding those of the natural silkworm silks, spider dragline silks and most other previously reported regenerated silk fibers. We believe that the high-performance silk-based fibers are promising applications in lightweight and advanced structural materials.

Heterostructure enables anomalous improvement of cryogenic mechanical properties in titanium

The pursuit of strong and ductile structures for cryogenic applications has fueled a persistent interest in the microstructure design of metals and alloys. While heterostructure design has recently demonstrated efficacy in achieving superior strength-ductility combinations at room temperature, its potential remains less explored in the cryogenic regime. In this report, we unveil anomalously improved cryogenic mechanical properties of a pure titanium with harmonic heterostructure that matches or even surpasses those of commercial titanium alloys. Through detailed comparison to room-temperature deformation behavior, we reveal that the superior performance of heterostructure at cryogenic temperature is fundamentally underpinned by the amplified inter-zone mechanical incompatibility and the suppression of dislocation cross-slip. The former promotes the generation of abundant geometrically necessary dislocations, and the latter optimally configures them. Collectively, these two factors culminate in the hetero-deformation-induced effect, delivering the anomalous improvement of cryogenic mechanical properties in titanium. These findings not only significantly advance our understanding of cryo-deformation behaviors in heterostructured materials but also offer the potential for developing high-performance materials for cryogenic applications.

The feasibility of resistance seam welding as an additive manufacturing technology for Al 1060

Resistance seam welding additive manufacturing (RSAM) is a new solid-state additive manufacturing technique that utilizes pulsed current and pressure to welding powders layer by layer. In this study, Al1060 powder was employed as the raw material to prepare R0 and R10 samples through RSAM technology and subsequent repeated welding processes, respectively. The results showed that, compared to R0, the grain size of the R10 sample decreased from 34.3 μm to 8.7 μm, and the dislocation density increased from 4.355×1014 to 9.436×1014 m-2. Additionally, due to the additional heat and pressure from repeated welding, the porosity decreased from 0.998% to 0.017%, the ultimate tensile strength and elongation improved from 63.5±0.5 MPa and 4.5±0.1% in R0 to 93.3±0.5 MPa and 34.3±0.1% in R10. The improvement in mechanical properties is primarily due to the combined effects of grain refinement, dislocation strengthening, and pore self-healing. This study introduces a feasible new approach for additive manufacturing of aluminum alloys and other materials that is difficult to be additively manufactured by other methods.

Chitosan-based nanocomposite films with carnauba wax, rosin resin, and zinc oxide nanoparticles

This work aimed to develop edible emulsion-based barriers in the form of chitosan composite films, with a focus on assessing the impacts of carnauba wax, rosin resin, and zinc oxide nanoparticles on their properties. Six films were produced by casting using chitosan as polymer base and glycerol as plasticizer. Acetic acid and polysorbate 80 were also used to facilitate the dissolution and mixing of the components. The six filmogenic solutions contained chitosan at 1.2% w/v, wax or resin content with 0 or 0.6% m/v and ZnO with 0 or 0.05% m/v. The dried films were characterized according to their chemical, barrier, mechanical, thermal and optical properties. All treatments resulted in flexible films. Chitosan films appeared smoother and more uniform under SEM imaging, while carnauba wax films displayed roughness due to their hydrophobic nature. Wax and resin films were less transparent and water soluble than the chitosan-only films. On the other hand, the addition of ZnO in the formulations increased the solubility of the films. The sorption degree was in line with the solubility results, i.e., films with ZnO presented higher sorption degree and solubility values. All treatments showed low or non-light UV transmission, indicating that the films provide good barrier to UV light. In the visible light region, films of resin with ZnO showed the lowest transmittance values, hence offering a good barrier to visible light. Among the evaluated films, chitosan, and resin films with ZnO nanoparticles were more rigid and resistant to deformation. Overall, films produced with rosin resin and ZnO nanoparticles showed potential improvements in barrier, mechanical, thermal, and optical properties, mainly due to their low water solubility, good UV protection and low permeability to water vapor and oxygen, which are suitable for using in formulations, intended to produce edible films and coatings

Simultaneous improvement of mechanical and castability properties of Al-Cu-Mn based alloys by Ca/Ni micro-alloying

Currently one major barrier for the design of cast high-strength and high-toughness Al alloys is hot tearing. In this work, a strategy of combination of squeeze casting and microalloying (Ca/Ni eutectic elements) in Al-Cu-Mn based alloys was employed to inherit the excellent mechanical properties of Al-Cu alloys whilst simultaneously reducing their tendency to hot tearing. The developed alloys exhibit comparable castability (fluidity and hot tear resistance) to A356, which is widely available commercially. However, their comprehensive mechanical properties far exceed those of A356. Trace Ca/Ni additions markedly reduce the grain size of the alloy and simultaneously increase the fraction of intergranular low melting point eutectic liquid phases, which is beneficial to the improvement of liquid feeding. The fine equiaxed grains have excellent thermal shrinkage coordination, while the high volume fraction eutectic liquid phase delays the development of grain cohesive skeleton. Accordingly, the localized shrinkage stress/strain at the hot spot is released timely, thus inhibiting the emergence and propagation of hot cracks in the brittle solidification interval. The diminished hot tearing susceptibility is attributed to the reduced load onset temperature and load values in the hot spot region. A new intergranular bridging mechanism is discovered in low-Ca alloys: based on compositional segregation-induced nucleation of an intergranular bridging skeleton, which strengthens the intergranular adhesive force and effectively reduces the hot tearing tendency of the alloys. The alloys with high-Ca/Ni additions, however, reduce the hot tearing tendency by healing cracks through eutectic liquid phase backfill. The results of the hot tearing experiments of the developed alloys are analyzed with the current hot tearing evaluation criteria. The results demonstrate that the predictions of the Kou's criterion provide guidelines for the design of alloys that are resistant to hot tearing.

Synergistic improvement of mechanical and piezoelectric properties of the flexible piezoelectric ceramic composite and its high-precision preparation

Flexible piezoelectric ceramic composites (FPCCs) hold promising applications in fields such as flexible sensing and energy harvesting. However, the previous methods are difficult to achieve high-precision preparation of the FPCCs with complex structures, as well as the synergistic enhancement of piezoelectric performance and flexibility. In this study, by configuring a flexible resin matrix and employing a surface functionalization treatment on the piezoelectric ceramic particles, the flexibility and piezoelectric performance of the FPCCs are synergistically improved. Moreover, the addition of a light absorber, TiO2, significantly improves the 3D printing precision. The mechanical properties, piezoelectric performance, and printing precision of the FPCCs are analyzed. It is found that the printing error is less than 2 μm, the tensile fracture strength is 4.07 MPa, the elongation at break is 350 %, and the piezoelectric constant d33 can reach 7.7 pC/N. In addition, the cyclic loading tests show that FPCCs with high-precision 3D complex microstructure have good recovery performance. This study not only enriches the formulation of FPCCs slurry for 3D printing, but also provides a research foundation for the multifunctional applications.

Prediction of grain boundary strength and mechanical responses of high-entropy carbides reinforced by hybrid graphene and SiC nanowire

The excellent performance of high entropy ceramics (HECs) has attracted extreme attention in the most advanced functional applications and engineering structures, yet the poor toughness limits the application of HECs in many fields. As a consequence, advanced technology and new doping phases are urgently demanded to enhance the comprehensive mechanical properties of HEC composites. The microstructure model of 0.2 wt% graphene (G) and SiC nanowires (SiCnw) doped in (HfNbTaTiZr)C is established in Abaqus with Python language. The effects of HEC-HEC interface strength and HEC-G interface strength on crack propagation and mechanical properties of HEC composites were investigated. The improvement of mechanical properties of (HfNbTaTiZr)C with different content of SiCnw was predicted respectively. The composites obtain the optimal combination of mechanical properties at the content of 1.5 wt% SiCnw. The accuracy of the simulation is verified by the experimental data of mechanical properties changing trend and toughening mechanism, providing theoretical support for toughening HEC composites.

Water Absorption, Thermal, and Mechanical Properties of Bamboo Fiber with Chopped Glass Fiber Filler-Reinforced Polyester Composites

This study explores the investigations of bamboo fiber-reinforced polyester composites with chopped glass fiber (CGF) filler, focusing on addressing the challenges of low mechanical properties, limited thermal stability, and high moisture absorption. The two types of composites were fabricated using the hand layup method, that is, long unidirectional 0° bamboo fiber (BF) and randomly oriented short bamboo fiber (BP) reinforced a polyester matrix with chopped glass fiber (CGF) filler. By incorporating CGF filler, significant improvements in mechanical properties were achieved across both types of bamboo fiber, surpassing the limitations of unfilled composites. Notably, the composite formulation consisting of 40% wt. of unidirectional 0° BF and 5% wt. of CGF filler exhibited superior ultimate tensile strength, flexural strength, impact strength, water absorption, and thermal stability. This composite demonstrated remarkable enhancements, with increases of up to 131.22 MPa, 128.76 MPa, 113.3 kJ/m2, 1.94% water absorption, and up to 255°C (representing a 10% improvement) in thermal stability compared to the unfilled composite. Statistical analysis revealed quadratic models for the mechanical properties of long unidirectional 0° bamboo fiber composites, while water absorption exhibited a linear two-factor interaction model. For randomly oriented short bamboo fiber, the models for tensile, flexural, and water absorption properties were linear, while the impact energy model showed a quadratic relationship. These statistical models provide valuable insights into predicting the properties of bamboo fiber-reinforced polyester composites. This research underscores the significance of bamboo fiber-reinforced polyester composites in wall partition systems. This study paves the way for improved performance in these areas. The findings highlight the potential of incorporating CGF filler, enabling enhanced mechanical strength, increased thermal stability, and improved resistance to moisture-related issues. The derived statistical models offer valuable guidance for predicting the properties of these composites, facilitating their application and adoption in the construction industry.

Addition of sodium carbonate to reinforce unglazed ceramic tile

Nowadays, the study of the improvement of mechanical properties is of great importance in the ceramic industry. The strenuous demand to which industrial processes are subjected leads to the search for new raw materials in the production lines that transfer superior characteristics to the finished product, standing out in the search for non-synthetic raw materials of mineral origin that contribute greater savings when added to the manufacturing process of the material. This study is focused on the use of sodium carbonate as an alternative raw material in the process of making ceramic tiles, sodium carbonate was obtained from two sources, one synthetic (soda ash) and the other mineral (trona). Within the research, additions of 0.15, 0.30, 0.45% of soda (Na2CO3) and 0.30, 0.60 and 0.90% of trona were made in the formulation of the ceramic body and properties such as density, compressive strength and modulus of rupture were evaluated. The results obtained indicate an improvement of up to 65% in the compressive strength when adding 0.9% of the trona and a 30% increase in the modulus of rupture thanks to the insertion of sodium carbonate.

Fabrication and property characterization of biocomposite based on polyamide 11 and AP1 green ramie fiber modified with epoxy

AbstractIn this article, Vietnam ramie fiber from Moc Chau, Son La province was chosen as a reinforcement for polyamide 11 (PA11) to prepare full–biocomposites. To enhance the compatibility and adhesion with the matrix, the original ramie fiber (oRF) was treated with Ca(OH)2 solution (tRF) and then modified by epoxy (mRF). Properties and structure of these fibers were characterized by tensile test, chemical composition, Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The obtained results showed the removal of hemicellulose and lignin after treatment improved the morphology and mechanical properties of the fiber. Rheology in melting state indicated the increase in the torque of PA11 matrix by adding tRF and mRF. The improvement in mechanical properties was observed for both PA11/tRF and PA11/mRF composites. After modification, epoxy on the fiber surface enhanced the adhesion and compatibility with the matrix. This led to a strong increase in Young's modulus, tensile strength and flexural strength of about 37%, 57%, and 33%, respectively. tRF and mRF also improved thermal stability of the composite as shown in TGA and DSC analysis. Finally, mRF showed a better compatibility with PA11 than tRF by observation of SEM images.

Thermo-mechanical behaviours investigation of Nano-Sized Al2O3, TiO2, and Graphene Nanoplatelet Reinforced Epoxy Composites

Composite materials find extensive applications in various industries, thanks to their remarkable properties. These sectors include energy, maritime, motor sports, aviation, space and defense. The materials commonly used in these sectors are fiber reinforced plastic (FRP) composite materials. Epoxy materials are commonly used as matrix in the production of FRP materials. This study delves into the enhancement of epoxy-based nanocomposites by using graphene nanoplatelets (GNP-5nm), TiO2 (13nm), and Al2O3 (8nm) nanoparticles. These nanoparticles were added at varying mass ratios into a commercial epoxy to investigate their effects on some chemical, thermal and mechanical properties. Meticulous mixing methodologies were used to reduce clumping effects and ensure even distribution during the process. The curing process was carried out in a PLC (Programmable Logic Controller) controlled hot air oven under isothermal conditions under the influence of 100 °C for 30 minutes. Tensile strength, elongation at break, toughness, resilience modulus, elasticity modulus, hardness, FTIR analysis and thermal conductivity properties were characterized to assess the nanoparticle influence on the epoxy matrix. The results showed that there were remarkable improvements in mechanical properties with nanoparticle reinforcement. Especially, 1.25% Al2O3 inclusion exhibited a substantial increase of 140.32% in tensile strength and a 7% rise in shore D hardness compared to pure epoxy. This enhancement was attributed to enhanced O-H bonding between 'O' atoms in Al2O3 nanoparticles and epoxy polymer chains, enhancing matrix-filler interactions. Additionally, the effect of 1.0% TiO2 led to plasticity, displaying a 32% rise in elongation at break, signifying improved deformation energy absorption compared to neat epoxy. In thermal conductivity measurements, the highest thermal conductivity was observed in the sample with 1.25% GNP added and it increased by 123.5% compared to neat epoxy. In TiO2 and Al2O3 added samples, an increase of 69% and 47%, respectively, was observed at 1.25% additive rates compared to neat epoxy. According to the results, thanks to the nanoparticle reinforcement added into the epoxy matrix, composite structures can be given new and superior properties specific to the applications.

Enhancing mechanical properties and defects elimination in 2024 aluminum alloy through interlayer friction stir processing in wire arc additive manufacturing

In this study, a hybrid wire arc additive manufacturing (WAAM) and interlayer friction stir processing (IFSP) approach was utilized to enhance the quality of 2024 aluminum alloy components. The defects characteristic, microstructure evolution, and mechanical properties of the fabricated components and after T6 heat treatment were analyzed systematically. Our analysis reveals that IFSP can break and dissolve the eutectic phases, significantly reduce porosity defects and refine the grain size of the as-deposited materials, thus improving the overall mechanical properties. Notably, compared to the WAAM as-deposited component, the yield strength (YS) and ultimate tensile strength (UTS) in the top-layer stir zone (SZ) of IFSP component increased from 154 ± 3 to 267 ± 2 MPa, and from 258 ± 12 to 360 ± 3 MPa, respectively. However, in the middle-layer SZ, S-phase precipitation and coarsening induced by thermal cycling during additive manufacturing slightly reduced the tensile properties. Post-T6 heat treatment led to uniformly distributed properties in the IFSP component along both horizontal and vertical directions, with the YS, UTS, and elongation (EL) averaging 353 ± 9 MPa, 470 ± 4 MPa, and 10.5 ± 1.6%, closely matching those of wrought counterparts. The significant improvements in mechanical properties are primarily attributed to the elimination of porosity and precipitation of fine needle-like S-phase. This research not only demonstrates the potential of IFSP in enhancing the mechanical properties of WAAM-fabricated 2024 aluminum alloy but also offers a promising technique for producing high-quality components suitable for high-performance aerospace applications.

Synergistic effects of silane‐modified carbon black and nano‐silica hybrid fillers on the performance of natural rubber compounds

AbstractThis study investigates the efficiency of already developed surface‐modified carbon black (CB), both independently and in conjunction with nano‐silica, as a hybrid filler, to the properties of natural rubber (NR) compounds. The modification process, followed by coupling agent treatment, enhanced cross‐link density and curing characteristics, though the inclusion of nano‐silica alone negatively affected curing due to its inherent polarity and tendency to agglomerate. The filled compounds with modified CB exhibited significant improvements in mechanical properties, notably tear resistance. Moreover, the combination of nano‐silica with modified CB yielded compounds with superior tear resistance, attributed to synergistic effects. CB surface modification exhibited varying effects on the glass transition temperature, with enhancements observed in tan δ at lower temperatures, indicating improved ice and wet grip potential. Also, it reduced rolling resistance after treatment with a coupling agent. While thermal stability remained consistent across the studied compounds, swelling resistance varies with filler type and ratio. Thermodynamic analysis confirmed the positive impact of CB surface modification on the elasticity and chain mobility of the investigated rubber compounds. It was concluded that the strategic selection of fillers and modification approaches were essential for achieving optimal results in the rubber compound's performance and application.

Crack-free hard facing options for orifice plate used in oil refinery applications

The purpose of this study is to select a suitable tubular wire electrode as an alternative hardfacing material for Stellite 1 in the production of SS304 orifice plates used in oil refineries. It is also intended to develop an efficient deposition procedure for crack-free hardfacing. Compatible cobalt, nickel, and iron-based hardfacing alloys were selected so as to match the hardness and hot hardness properties of stellite 1. Moving heat source analysis was performed to find the heat affected zones and the thermal stress distribution during hardfacing. The significance of weld speed, bead width, and weld concentration on the weld deposition process was analysed using ANSYS, to extract an efficient deposition procedure. The hardfacing alloys were tested for stress and deformation at working temperature (up to 815 οC) to understand the performance. Seven materials were taken into consideration as options along with six parameters. The results revealed a higher longitudinal residual stress of 2000 MPa for Talonite and Tribaloy hardfacing alloys. Colmonoy 6 was found to be having the least stress value of 2186 MPa. Furthermore, the von mises stress values arrived for different conditions showed that the optimal welding condition is 5 mm/s welding speed, 3 mm radius of beam and 455 °C preheat temperature. Microstructural study revealed the dendrite growth in the surface of Colomony 6 hardfacing during solidification, which led to the improvement in mechanical properties.

Multi-Objective Optimization for Seismic Structural Investigation and Maintenance Strategies of Bridges in Service

With the continuous updating of seismic design codes for Bridges, the new regulations have higher requirements for the seismic structure and mechanical properties of old Bridges. In order to make the decision of seismic structure strengthening more scientifically, with the goal of optimal overall performance, minimum economic cost and minimum environmental impact, the optimal model of seismic strengthening sustainable strategy is established. Firstly, according to the results of the seismic measures of the existing Bridges, the corresponding reinforcement measures are proposed for the structural problems that do not meet the seismic measures. Then the utility evaluation of the three objectives of the existing bridge was carried out. At last, NSGA-Ⅱ algorithm was used to build a multi-objective maintenance decision optimization model of the bridge network. Combined with the weight of the decision-maker's preference, TOPSIS algorithm was used to obtain the optimal solution of the target, and decision-making suggestions were provided for the relevant departments. The results show that there are many structural problems in the new evaluation of the old bridge, and the maintenance of the structural problems are more feasible and effective than the improvement of the traditional mechanical properties. Combined with the comprehensive evaluation utility and reinforcement objective function, the maintenance decision can be better under different objectives. The reinforcement maintenance decision model has the ability to improve the comprehensive performance and sustainability of the bridge to the maximum extent within the limited budget.

Influence of Ceramic Wastes as a Recycled Coarse Aggregate with Different Maximum Sizes on the Concrete

Background Natural raw resources needed for concrete construction are continuously being depleted as a result of infrastructure development that is increasing. As a result, waste material substitutes are highly favored because they adopt a sustainable strategy. Objective In this study, the possibility of substituting natural coarse aggregates with coarse aggregate made from ceramic wall tiles with three different maximum aggregate sizes (12.5, 19, and 25 mm) in three partial replacement levels of natural coarse aggregate by (25, 50, and 75%) was investigated. Methods Concrete's hardened density, compressive and splitting tensile strengths, ultrasonic pulse velocity, water absorption, and volume of permeable pores were all tested experimentally. Results Results indicated that with the increment of the maximum aggregate size, each of the hardened densities, the compressive and splitting tensile strengths and the rate of water absorption diminished while pulse velocity enhanced, regardless of the substitution rate of ceramic aggregate. However, for all maximum aggregate sizes, the mixture containing 25% ceramic coarse aggregate showed a small improvement in mechanical properties. Compared to the reference mixture, which had compressive strengths of 29.31, 38.73, and 47.13 MPa at 7, 28, and 90 days for the 12.5 mm maximum aggregate size, the improvement ratios were 8.9%, 3.7%, and 2.7% at 7, 28, and 90 days, respectively. Moreover, because of increased heterogeneity, internal bleeding, and the development of microcracks in the larger coarse aggregate sizes, concrete with lower ceramic coarse aggregate sizes has a stronger bond than that of the latter. Results also indicated that the mechanical performance of concrete mixtures having ceramic aggregate slightly improved with 25% ceramic coarse aggregate, then lowered in the mixtures with 50% and 75%, consecutively, at all ages. Concrete using ceramic aggregate displays a poor transition zone because of the improper binding between the paste and the coarse ceramic aggregate caused by the aggregate's porcelain texture. Additionally, the water absorption of concrete mixtures containing ceramic aggregate increased with the increase in the percentage of ceramic coarse aggregate. Conclusion The employing of ceramic waste aggregate was shown to contribute to sustainable development and a cleaner environment by producing sustainable concrete from the recycling of ceramic wastes. Each of the hardened density, compressive strength, splitting tensile strength, and water absorption of concrete mixtures decreased and the pulse velocity enhanced as the maximum aggregate size increased. The mechanical properties decreased at all ages in the mixtures containing 50 and 75% of the aggregate, whereas they slightly increased in the mixture containing 25% of the aggregate.

Effect of Deep Cryogenic Aging Treatment on Microstructure and Mechanical Properties of Selective Laser-Melted AlSi10Mg Alloy

Deep cryogenic aging (DCA) is a newly developed heat treatment technique for additive-manufactured metallic materials to reduce residual stress and improve their mechanical properties. In this study, AlSi10Mg alloy samples fabricated by selective laser melting were deep-cryogenic-treated at −160 °C and subsequently aged at 160 °C. Phase and microstructural analyses were conducted using X-ray diffraction, optical microscopy, scanning electron microscopy, and transmission electron microscopy, while the mechanical properties were evaluated through microhardness and tensile testing at room temperature. The results indicated that the DCA treatment did not have an effect on the morphology of the melt pools. However, it facilitated the formation of atomic clusters and nanoscale Si and β′ phases, as well as accelerating the coarsening of grains and the ripening of the eutectic Si phase. After DCA treatment, the mass fraction of the Si phase experienced an increase from 4.4% to 7.2%. Concurrently, the volume fraction of the precipitated secondary phases elevated to 5.1%. The microhardness was enhanced to 147 HV, and the ultimate tensile strength and yield strength achieved 495 MPa and 345 MPa, respectively, with an elongation of 7.5%. In comparison to the as-built specimen, the microhardness, ultimate tensile strength, and yield strength increased by 11.4%, 3.1%, and 19.0%, respectively. The improvement in mechanical properties is primarily attributed to the Orowan strengthening mechanism induced by the secondary phases.

In situ growth of Ag nanoparticles on the surface of MXene by γ-ray irradiation to fabricate EVA composite: The improvement of flame retardancy, smoke suppression, and mechanical properties

Abstract A large amount of toxic smoke and heat generated by the combustion of ethylene vinyl acetate copolymer (EVA) poses a significant threat to human fire escape evacuation. This work aims to use γ-ray to prepare e-MXene@Ag hybrid flame-retardant materials by the method of in-situ reduction, and EVA composites are prepared by melt blending to reduce the smoke and toxic gases produced during combustion significantly. Compared with pure EVA, the total heat release, total smoke release, and the production rate of CO and CO2 produced by the combustion of EVA composite with 1wt% e-MXene@Ag1.0 decreased by 30.3%, 33.3%, 18.2%, and 20.1% respectively, while the content of residue increased by 907.4%. The fire hazard reduction of EVA composite materials was due to the physical barrier, catalytic carbonization and adsorption of the e-MXene@Ag1.0 hybrid. In addition, e-MXene@Ag1.0 can also further increase the mechanical properties of EVA composites due to its own "multi-contact point limit structure."