Mechanical Properties Of Materials Research Articles

Verification of the Laser Powder Bed Fusion Performance of 2024 Aluminum Alloys Modified Using Nano-LaB6

The application of 2024 aluminum alloy (comprising aluminum, copper, and magnesium) in the aerospace industry is extensive, particularly in the manufacture of seats. However, this alloy faces challenges during laser powder bed fusion (PBF-LB/M) processing, which often leads to solidification and cracking issues. To address these challenges, LaB6 nanoparticles have been investigated as potential grain refiners. This study systematically examined the impact of adding different amounts of LaB6 nanoparticles (ranging from 0.0 to 1.0 wt.%) on the microstructure, phase composition, grain size, and mechanical properties of the composite material. The results demonstrate that the addition of 0.5 wt.% LaB6 significantly reduces the average grain size from 10.3 μm to 9 μm, leading to a significant grain refinement effect. Furthermore, the tensile strength and fracture strain of the LaB6-modified A2024 alloy reach 251 ± 2 MPa and 1.58 ± 0.12%, respectively. These findings indicate that the addition of appropriate amounts of LaB6 nanoparticles can effectively refine the grains of 2024 aluminum alloy, thereby enhancing its mechanical properties. This discovery provides important support for the broader application of 2024 aluminum alloy in the aerospace industry and other high-performance fields.

Recycling and reuse of waste banded iron formation as fine aggregate in the production of lightweight foamed concrete: Fresh-state, mechanical, thermal, microstructure and durability properties assessment

This study investigates the possibility of using BIFs as sustainable fine aggregates to produce lightweight foam concrete (LWFC) by replacing sand with 5, 10, 15, 20, and 25 % banded iron formations (BIFs). The fresh concrete properties, such as slump flow, density, and setting time, as well as its mechanical properties, including compressive strength, splitting strength, and flexural strength, were investigated. The thermal conductivity, specific heat, porosity, gas permeability, pore distribution, and sorptivity were measured to determine durability and thermal performance. Microstructural analysis of the mixes was performed using SEM, energy-dispersive X-ray spectroscopy (EDX), and mapping. The results recommended a 10 % replacement ratio to achieve an increased compressive strength ratio of 55.88 % compared to the control mix at 7 days (d). The strength at later ages increased compared to that of the control mix by 33.9 %, 30 %, 42.48 %, and 42.4 % at 14, 28, 56, and 180 d, respectively. In addition, the flexure increased by 42.7 % at 7 d, 49.6 % at 14 d, and 45.6 % at 28 d compared to the control mix. In addition, the UPV also increased gradually from 2757 to 3699 km/s with increase in BIFs content. Furthermore, the porosity decreased at 7 d, 14 d, 28 d, and 90 d. Moreover, chloride penetration decreased by 2.5 %, where an improvement in thermal conductivity was achieved with BIFs to 0.342 W/mK compared to that of the control mix. In addition, a reduction in the specific heat of the material from 1042 J/kg K to 1007 J/kg K was observed. SEM showed a better arrangement of pores when BIFs were utilized compared with that of control mix without BIFs. In conclusion, the incorporation of waste BIFs as fine aggregates in lightweight foam concrete demonstrates a promising potential for enhancing the mechanical and thermal properties of construction materials, paving the way for durable building materials in the construction industry.

Toughness Evolution of Flax-Fiber-Reinforced Composites under Repeated Salt Fog-Dry Aging Cycles.

This research examined the response of flax-fiber-reinforced composites (FFRCs) to simulated outdoor conditions involving repeated exposure to salt fog and drying. The study investigated the effect of cycles on the toughness of the FFRCs. To achieve this, the composites were exposed to humidity (salt fog) for 10 days, followed by 18 days of drying in cycles. A total of up to 3 cycles, each lasting 4 weeks, were conducted over a 12-week period. Throughout this process, changes in the material's weight, water absorption, and mechanical properties were monitored by water uptake and three-point bending tests. The findings revealed the significant impact of these humid-dry cycles on the mechanical response of the FFRCs. When exposed to humid environments without drying, the composite's toughness increased significantly, due to a weakening effect more pronounced for stiffness, with strength reductions of about 20%. However, subsequent drying partially restored the material's performance. After 18 days of drying, the composite regained most of its initial performance.

Shear Strengthening of Stone Masonry Walls Using Textile-Reinforced Sarooj Mortar

Most historical buildings and structures in Oman were built using unreinforced stone masonry. These structures have deteriorated due to the aging of materials, environmental degradation, and lack of maintenance. This research investigates the physical, chemical, and mechanical properties of the local building materials. It also presents the findings of an experimental study on the in-plane shear effectiveness of a modern strengthening technique applied to existing stone masonry walls. The technique consists of the application of a textile-reinforced mortar (TRM) on one or two faces of the walls. Shear loading tests of full-scale masonry samples (1000 mm width, 1000 mm height, and 350 mm depth) were carried out on one unreinforced specimen and six different cases of reinforced specimens. The performances of the unreinforced and reinforced specimens were analyzed and compared. We found that strengthened specimens can resist in-plane shear stresses 1.5–2.1 times greater than those of the unreinforced specimen; moreover, they demonstrate ductility rather than sudden failure, due to the presence of fiberglass and basalt meshes, which restrict the opening of cracks.

Shear Strengthening of Stone Masonry Walls Using Textile-Reinforced Sarooj Mortar

Most historical buildings and structures in Oman were built using unreinforced stone masonry. These structures have deteriorated due to the aging of materials, environmental degradation, and lack of maintenance. This research investigates the physical, chemical, and mechanical properties of the local building materials. It also presents the findings of an experimental study on the in-plane shear effectiveness of a modern strengthening technique applied to existing stone masonry walls. The technique consists of the application of a textile-reinforced mortar (TRM) on one or two faces of the walls. Shear loading tests of full-scale masonry samples (1000 mm width, 1000 mm height, and 350 mm depth) were carried out on one unreinforced specimen and six different cases of reinforced specimens. The performances of the unreinforced and reinforced specimens were analyzed and compared. We found that strengthened specimens can resist in-plane shear stresses 1.5–2.1 times greater than those of the unreinforced specimen; moreover, they demonstrate ductility rather than sudden failure, due to the presence of fiberglass and basalt meshes, which restrict the opening of cracks.

Nonlinear resonant responses of a novel FGM sandwich cylindrical shell structure for supersonic flight vehicles based on 1:1 internal resonance between conjugate modes

A new design scheme for the functionally graded material (FGM) sandwich cylindrical shell structure made of ceramic-FGM-carbon fiber composites is proposed, which is geared towards supersonic flight vehicles and has high specific stiffness and high-temperature resistance. We focus on analyzing the nonlinear resonant responses of the novel FGM sandwich cylindrical shell subjected to external excitation and aerodynamic force. Firstly, the mechanical properties of the novel FGM sandwich material are calculated, and then the nonlinear dynamic model of the FGM sandwich cylindrical shell is established based on the first order shear deformation theory (FSDT) and Hamilton's principle. Due to the axisymmetric property of the cylindrical shell, a 1:1 internal resonance between the driven and companion modes always exists in the perfect cylindrical shell. Taking this into consideration, the nonlinear resonant response problems of the FGM sandwich cylindrical shell are numerically simulated by combining the Galerkin method and the pseudo-arc length continuation method. Finally, the effects of complex parameters such as external excitation, aerodynamic force, aspect ratio, gradient index, and skin-core-skin ratio on the nonlinear resonant responses of the FGM sandwich cylindrical shell are investigated.

Hardening properties and microstructure of 3D printed engineered cementitious composites based on limestone calcined clay cement

Comparison of three-dimensional (3D) printing and cast methods on the mechanical properties of cementitious materials is the basis for intelligent construction development. To achieve this, a series of experiments including the uniaxial tensile, compressive, flexural and interlayer bonding tests of mould-cast and 3D printed (3DP) specimens are conducted to investigate the effects of different preparation technologies on the microstructure and hardening properties of limestone calcined clay cement (LC3) based engineered cementitious composites (ECC). Results indicate that the tensile strength and strain capacity of the printed LC3-ECC decrease by 16.6%–22.7 % and 43.3%–54.6 % compared to the cast specimens, while it still possesses a strain capacity of 2 % and multiple cracking behaviour. The compressive and flexural properties of the printed LC3-ECC both show significant anisotropy, the maximum values of which are observed in the Z- and Y- directions, respectively. The interlayer bonding strength increases by 54.3%–91.9 % at 28 d compared to that at 7 d due to the hydration of LC3. The pore structure of the printed LC3-ECC is denser than that of the cast LC3-ECC, with more regular arrangement and finer size of pores. The macro-micro properties correlation analysis proves the better comprehensive performance of printed LC3-ECC relative to casted LC3-ECC, as well as reveals the relationship between pore structure and anisotropy. In terms of material sustainability, 3DP-LC3-ECC has a significant reduction in energy and carbon emissions compared to typical M45-ECC, contributing to the environmental development.

Flexibility, toughness, and load bearing of 3D-printed chiral kerf composite structures

Chiral kerf structures are formed by arranging chiral and coiled unit cells which allows for multi-dimensional and multi-scale shape configurations under mechanical loadings. In this study, we investigate how the mechanical properties of materials and microstructural topologies interact to control the flexibility, toughness, and load bearing of 3D-printed chiral kerf structures. We explore chiral kerf structures with two different kerf patterns, i.e., square and hexagon, and three coiling densities. We consider three materials, namely brittle Polylactic Acid (PLA), compliant thermoplastic polyurethane (TPU), and a ductile composite made by alternating PLA and TPU, referred to as a programmable composite. The chiral kerf structures undergo two deformation mechanisms when subjected to mechanical loadings. The first one results from reconfigurations of kerf cells such as uncoiling, rotation of cells, and cell packing, and the second mechanism arises from nonlinear and inelastic material responses. The use of brittle material limits cell reconfigurations before material failure, reducing the overall flexibility and toughness of kerf structures. While the compliant material enables full cell reconfigurations, it results in low load bearing. The use of PLA:TPU composite allows for cell reconfigurations and inelastic material response, enhancing flexibility and toughness while maintaining a relatively high load bearing. We demonstrate that stress distribution in kerf structures can be controlled by using multiple materials or coil densities. This strategy can delay failure and improve the toughness and load-bearing capabilities of kerf structures.

Synergy of Hybrid Fillers for Emerging Composite and Nanocomposite Materials-A Review.

Nanocomposites with polymer matrix provide tremendous opportunities to investigate new functions beyond those of traditional materials. The global community is gradually tending toward the use of composite and nanocomposite materials. This review is aimed at reporting the recent developments and understanding revolving around hybridizing fillers for composite materials. The influence of various analyses, characterizations, and mechanical properties of the hybrid filler are considered. The introduction of hybrid fillers to polymer matrices enhances the macro and micro properties of the composites and nanocomposites resulting from the synergistic interactions between the hybrid fillers and the polymers. In this review, the synergistic impact of using hybrid fillers in the production of developing composite and nanocomposite materials is highlighted. The use of hybrid fillers offers a viable way to improve the mechanical, thermal, and electrical properties of these sophisticated materials. This study explains the many tactics and methodologies used to install hybrid fillers into composite and nanocomposite matrices by conducting a thorough analysis of recent research. Furthermore, the synergistic interactions of several types of fillers, including organic-inorganic, nano-micro, and bio-based fillers, are fully investigated. The performance benefits obtained from the synergistic combination of various fillers are examined, as well as their prospective applications in a variety of disciplines. Furthermore, the difficulties and opportunities related to the use of hybrid fillers are critically reviewed, presenting perspectives on future research paths in this rapidly expanding area of materials science.

Microstructure, Texture, and Mechanical Properties of 0.4GNPs–Mg–8Al–1Sm Composites Prepared by Pulse Current‐Assisted Multidirectional Forging

The present study investigates the evolution of the microstructure and texture of a hot‐pressed sintered 0.4GNPs–Mg–8Al–1Sm (mass fraction, %) composite material during a pulsed current‐assisted multidirectional forging process. Additionally, this study explores the use of the pulse current‐assisted multidirectional forging mechanism for strengthening the mechanical properties of composite materials. The results indicate that as the cumulative strain (ΣΔε) increases, the amount of Mg17Al12 and Al2Sm gradually increases while their size decreases. Furthermore, the fraction of the recrystallization area increases. The recrystallization mechanism is dominated by continuous dynamic recrystallization and discontinuous dynamic recrystallization. The refinement of the alloy grain size is attributed to dynamic recrystallization. Specifically, at ΣΔε = 3.15, the compressive strength and fracture strain of the multidirectional forged 0.4GNPs–Mg–8Al–1Sm composite reach 461.5 MPa and 18.8%, respectively. By quantitatively analyzing the strengthening mechanism of the alloy, it is determined that fine‐grain strengthening is the most significant mechanism contributing to the strength of the 0.4GNPs–Mg–8Al–1Sm composite.

First-principles calculations of the electronic structure and thermodynamic properties of B–Co–O materials

In the present study, the structural properties, electronic, elastic, and thermodynamic properties of Co4B6O13、Co2B2O5、Co3(BO3)2、Co(BO2)2, and CoB4O7 materials were calculated by adopting first-principles calculation method based on density functional theory. The simulated lattice constant is compliant with the existing experimental data well. The formation energy, Gibbs free energy, and phonon dispersion curves show that the B–Co–O materials are thermodynamically stable. The results show that the mechanical properties of CoB4O7 material is excellent, while the mechanical properties of Co2B2O5 material is the weakest. The CoB4O7 material has higher Debye temperature and constant volume heat capacity, and the thermodynamic stability of Co3(BO3)2 is the best. By analyzing band structure and electronic density of states, Co2B2O5 and Co3(BO3)2 materials are conductors, Co4B6O13, Co(BO2)2 and CoB4O7 materials belong to P-type semiconductors. Through electronic density of states analysis and Hirshfeld analysis, they indicated that five B–Co–O materials exhibit ferromagnetic.

Machine learning approach to predict the mechanical properties of cementitious materials containing carbon nanotubes

This research explores the use of machine learning to predict the mechanical properties of cementitious materials enhanced with carbon nanotubes (CNTs). Specifically, the study focuses on estimating the elastic modulus and flexural strength of these novel composite materials, with the potential to significantly impact the construction industry. Seven key variables were analyzed including water-to-cement ratio, sand-to-cement ratio, curing age, CNT aspect ratio, CNT content, surfactant-to-CNT ratio, and sonication time. Artificial neural network, support vector regression, and histogram gradient boosting, were used to predict these mechanical properties. Furthermore, a user-friendly formula was extracted from the neural network model. Each model performance was evaluated, revealing the neural network to be the most effective for predicting the elastic modulus. However, the histogram gradient boosting model outperformed all others in predicting flexural strength. These findings highlight the effectiveness of the employed techniques, in accurately predicting the properties of CNT-enhanced cementitious materials. Additionally, extracting formulas from the neural network provides valuable insights into the interplay between input parameters and mechanical properties.

The effect of temperature on monocrystalline Si nanoindentation side effects: A molecular dynamics study

Monocrystalline Si materials has been widely used in the fields of micro-electro-mechanical systems and electronic chips. At the micro and nanoscale, there are differences in the mechanical properties at the workpiece side compared to its interior. Meanwhile, temperature also has a significant impact on the mechanical properties of materials. In this paper, to analyze the effect of the temperature on the nanoindentation side effect of monocrystalline Si, a series of molecular dynamics (MD) simulations of nanoindentation are performed under six different temperatures. The simulation results show that the plastic deformation behavior, indentation force, internal stress, and the Internal defects are closely related to the temperature in nanoindentation. This work attributes a better understanding of the temperature effect on the nanoindentation side effect of the monocrystalline Si materials.

Fabrication of bulk-sized W-1.1%TiC alloy with helium bubble retention via powder metallurgical route incorporated with helium ambient mechanical alloying

In the field of materials irradiation, it has been noted that incorporating helium (He) element into metals may have the beneficial effect of improving both strength and ductility in the high temperature region where creep occurs. In order to fabricate such new functional materials and apply them to a wide range of fields, it is necessary to establish new fabrication methods for bulk-size materials. In this study, bulk-sized W-1.1%TiC alloys containing He bubbles were fabricated by a powder metallurgical route using mechanical alloying in a He atmosphere and subsequent thermo-mechanical processing. Transmission electron microscopy observations showed that this fabrication process successfully incorporated nano-sized He bubbles into W-1.1%TiC. Since this fabrication process is free of radioactivation and irradiation-induced defects, it will facilitate research into the fundamental understanding of the independent effects of He bubbles on the physical and mechanical properties of various materials concerned.

The impact of nanoparticle surface topography on the interfacial mechanical behavior and microstructure of polyvinyl alcohol composites

The interfacial mechanical strength between nanoparticle and matrix is one of the key factors affecting the mechanical properties of nanoparticulate-polymer composites. Based on the structural composition of a nanoscale iron particle/polyvinyl alcohol composite, this study employed molecular dynamics simulations to investigate the stress-response behavior and microstructural evolution of Fe/PVA/Fe interface models with different surface morphologies under both tensile and shear deformations. The results indicate that when the particle surfaces exhibit different rough structures, the interfacial tensile strength significantly increases with the absolute value of the interfacial binding energy. The order of tensile strength is Type-cube > Type-pyramid > Type-plane. Furthermore, during the shearing process, the protruding structures on the particle surfaces significantly hinder the deformation and unfolding of the matrix molecular chains. As the volume of the protruding structures increases, the interfacial shear strength decreases markedly. The research findings illuminate the mechanisms by which nanoparticle surface morphology at the microscopic molecular scale influences the mechanical properties of nanoparticle-polymer composite materials. These discoveries aid in selecting nanoparticle fillers that enhance the mechanical performance of polymer nanocomposites to a measurable extent.

Study on the design method of multi-component industrial solid waste low carbon cementitious material with cement as the activator

The relationship between microstructure and mechanical properties of multi-component solid waste low-carbon cementitious materials has been widely pay attention to. However, industrial solid waste is a complex multi-component system with many variable factors, which makes it difficult to design the formulation of cementitious materials. This paper pioneered the application of machine learning (ML) models, algorithms and error rates to analyze the compressive and flexural strength of fly ash-based pastes. Coefficient of determination (R2), mean squared error (MSE), root mean square error (RMSE), mean absolute error (MAE) and a20-index were used to evaluate robustness. X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunauer-Emmett-Taylor (BET) were carried out to analyze evolution of cementitious materials. The evaluation results of ML models exhibited that the Gradient boosting regression (GBR) model had the best determination parameters and a steep normal distribution fitting curve with an a20-index of 0.861. GBR model exhibited the best robustness. The key factors of fly ash-based cementitious materials were identified by Pearson's coefficient, which was benefit to determine the formulation of multi-component solid waste low-carbon cementitious materials. Furthermore, experiments also demonstrated that the optimum ratio of multi-component solid waste low carbon cementitious material was 10 % gypsum, 10 % metakaolin, 45 % fly ash, 15 % slag and 20 % cement, respectively. It was worth noting that the compressive strength of this kind of multi-component solid waste low-carbon cementitious materials reached 35 MPa, which was superior to the mechanical properties of P·O 32.5 cement. The results of phase, SEM images and pore structure distribution showed that the synergistic effect of the multi-component solid waste materials effectively filled the material voids and also facilitated the formation of a variety of gelatinous materials through gelling reactions in the late stage (14–28 d). This work will promote the resource utilization of industrial solid waste, contribute to carbon reduction, and can accelerate the green revolution of concrete.

Pressure tuning of superconductivity in TiN thin films

Titanium nitride (TiN) thin films are used for the fabrication of superconducting devices due to their chemical stability against oxidization and high quality at interfaces. The high-pressure technique serves as a useful tool to understand the mechanical and electrical properties of materials, which is crucial for practical applications. However, high-pressure transport measurements of thin films are extremely difficult due to the limited sample space of high-pressure cells and the fragility of thin films. Here, we successfully carried out high-pressure electrical transport and Raman measurements on TiN films up to ∼50 GPa. The superconducting transition temperature gradually decreases with increasing pressure, which can be attributed to the decrease of electron -phonon coupling and is consistent with our first-principles calculations. In addition, the coexistence of a symmetry-enforced Dirac nodal chain and a nodal box is revealed by our calculations in TiN. Our work provides a promising way to study the physical properties of thin films at high pressure, which would broaden the high-pressure research field.

Constitutive model of die-cast light-alloy thin-walled parts considering geometric imperfection

Replacing steel with aluminum and shifting from forging to casting have become important means of automotive lightweight. Large integrated die-cast parts are gaining popularity among original equipment manufacturers. Engineers often ignore the influence of geometric imperfection on mechanical properties when simulating strength of thin-walled parts, therefore causing a bias. To investigate the relation between geometric imperfections and mechanical properties of die-cast light alloy, quasi-static tensile tests are conducted on the specimens of JDA1b aluminum alloy and JDM1 magnesium alloy. The specimens exhibit varying geometric imperfection factors (from 0 to 90%) achieved by introducing circular holes with different diameters. The results show that the strength and elongation of JDA1b and JDM1 alloys decrease significantly as the geometric defect factor increases. Even small holes can significantly affect tensile strength. A constitutive model that incorporates the stress limit value and geometric imperfection factors is proposed, which has higher accuracy than the J–C model. Experiments and simulations on a die-cast thin-walled part validated the idea and proposed constitutive model. These findings provide essential insights into the influence of structural holes on the mechanical properties of die-cast light-alloy materials. The proposed constitutive model offers high-precision computational support for simulating the mechanical performance of parts.

Mechanical properties of composite materials with low-covered polyrotaxane and plasma-surface-modified hexagonal boron nitride

An effective method for fabricating flexible materials containing thermally conductive fillers, such as hexagonal boron nitride (hBN), utilizes plasma surface modification and polyrotaxane (PR) with movable cross-linking points. This study demonstrated that lowering the coverage rates of PR composites increased the mobility of the cross-linking points. Plasma surface modification improved the dispersion of hBN and enabled homogeneous deformation of the PR composites owing to movable cross-linking points. Studying the deformation with a model including a finite extension effect indicated that the sliding range in the low-covered PR composites was extended compared to that in the high-covered PR composites, resulting in a smaller Young’s modulus, longer extension, and higher toughness.

Effect of nano-TiC/TiB2 and final thermo-mechanical treatment on microstructure and properties of 7185 alloy

In this study, a new generation of ultra-high strength 7185 aluminum alloy and nano-sized TiC+TiB2 particles reinforced 7185 alloy matrix composites (PRAMCs) were prepared, and its thermos-mechanical treatment (TMT) was studied. The electron probe microanalyzer, electron back scattered diffraction, and transmission electron microscope are used to study microstructure evolution. Tensile tests are used to investigate the mechanical properties of composite materials. The results showed that the grain can be refined significantly by adding particles. The grain size of the quenched state is very fine. The strength and plasticity of the alloy are significantly improved. After the final TMT, many dislocations were introduced, and the precipitation phase and dislocation intertwined with each other during the aging process. This increased the dislocation density and promoted the precipitation process. Thus, the strength and corrosion resistance are improved, but the plasticity is reduced. The yield strength, tensile strength, and elongation of the PRAMCs designed in this study after final TMT are 483.6MPa, 520.4MPa, and 9.1%, respectively. The inter-granular corrosion layer depth is 47.2 μm. The the grade of exfoliation corrosion for 6h and 24h is PC, and EA, respectively. This study can provide strategies for the performance optimization of PRAMCs.