Enhancement Of Mechanical Properties Research Articles

Polydopamine‐coated iron‐nickel alloy and epoxy composites for electromagnetic interference shielding

AbstractWith the development of electronic devices and wireless communication technology, the quality of human life has improved. However, shielding from electromagnetic interference (EMI) is required due to device malfunctions and harmful effects on human health. Polymer‐based shielding materials getting much attention due to their light weight, flexibility, good processability, and other desirable traits. However, achieving consistent dispersion of conductive fillers and optimizing the balance between electrical, mechanical, and thermal properties remain challenges despite the advantages of polymer‐based materials. Especially, epoxy resins are promising polymer materials for EMI shielding applications due to their excellent mechanical strength, chemical resistance, and excellent adhesive properties. Additionally, epoxy resin exhibits remarkable processability allowing for various fabrication techniques such as casting, molding, and three‐dimensional printing. However, one of the significant drawbacks of epoxy resin is the difficulty in achieving uniform dispersion of conductive fillers within the epoxy matrix. In this study, we propose an iron‐nickel alloy (FeNi) embedded in an epoxy matrix (FeNi/Epoxy) for EMI shielding material. It is manufactured by facile fabrication process due to the advantages of epoxy, which has excellent processability. EMI shielding effectiveness at 12 GHz is enhanced from 9.12 to 17.86 dB by the increase of FeNi concentrations. Furthermore, thermal and mechanical properties were improved by the increase of FeNi concentration. Thermal conductivity for efficient heat dissipation is increased from 0.63 to 1.49 Wm−1 K−1. Moreover, polydopamine (PDA) was employed as a surface coating material for FeNi to overcome the non‐uniform dispersion of FeNi particles in the epoxy matrix. Surface coating by PDA significantly enhanced the dispersion uniformity and strengthened the adhesion between the filler and matrix. Elastic modulus is greatly increased from 83.03 MPa to 1.29 GPa by the surface coating. The enhancement of mechanical properties is derived from the chemical bonds between the filler and matrix.

Enhancement of mechanical properties in coral concrete via seawater and sea-sand: Experimental insights into the use of dual plastic fibers

The South China Sea contains many coral reefs, and there is a lot of discussion about the best way to dispose of them. Finding ways to use these materials effectively in marine engineering could help address the shortage of natural aggregates in coastal engineering. One potential solution is using coral concrete, which offers cost-effective and enhanced properties. A type of coral fiber concrete using sea sand is created by combining coral rock, sea sand, seawater, PVA fiber, and PP fiber. The findings indicate that by utilizing the optimal ratio of the two fibers (3 kg PVA + 1 kg PP and 2 kg PVA + 2 kg PP), the cubic and axial compressive strength of the new concrete can be increased by 10 % and 20 %, respectively compared to ordinary coral concrete. Furthermore, incorporating these fibers can also reduce axial displacement, resulting in an elastic modulus that is 30–50 % higher than non-fiber variants while enhancing axial toughness. Finally, this study examines stress-strain curves at three different stages through analysis of macroscopic and microscopic failure mechanisms. It was found that there exists a correlation exceeding 0.9 between two mathematical models and measured stress-strain curves from this study. The effective use of composite plastic fiber significantly enhances concrete material performance while providing valuable data support for marine economic facilities construction.

Enhanced mechanical properties of the additively manufactured IN738LC superalloy through thermal history management during the laser powder bed fusion process

IN738LC superalloy, as one of the hard-to-weld Ni-based superalloys, is relatively difficult to be produced by laser powder bed fusion (LPBF) due to its high cracking susceptibility. In this study, local heat accumulation based on substrate preheating and chessboard scanning strategy modification was proposed to reduce the thermal stress and promote the dynamic precipitation of IN738LC superalloy during LPBF process, which contributes to the crack inhibition and mechanical property enhancement. The as-built IN738LC superalloy exhibited superior room temperature tensile yield strength (YS) of 1011 ± 7 MPa, ultimate tensile strength (UTS) of 1400 ± 12 MPa, and good ductility of 17.4 ± 2.9 %. The superior mechanical performance was achieved mainly due to the successful elimination of micro-cracks, the formation of hierarchical microstructure composed of columnar γ grains, cellular dislocation network, especially in-situ formation of carbide precipitates. The formation of micro-cracks was fully eliminated due to the reduced temperature gradient and residual stress. In-situ formation of carbide precipitates was enabled by well-controlling the thermal history during the LPBF process. The use of a chessboard scanning strategy and substrate preheating was found to be beneficial for achieving a larger melting pool size, coarser dendrite/cellular arm spacing, and a larger volume of carbide precipitates due to enhanced heat accumulation during the LPBF process, which was verified by finite element analysis. This work provides insights into the effects of thermal profiles inherent to LPBF processes on the performance of LPBF-processed IN738LC superalloy.

Enhancing Mechanical Properties of Cast Ingot Al6061 Alloy Using ECAP Process

AbstractGrain refinement and mechanical property enhancement of cast ingot aluminum 6061 alloy were achieved using equal-channel angular pressing (ECAP) at room temperature, employing route A and route R types. Analytical, finite element and experimental methods were utilized to investigate the alloy’s deformation behavior under the ECAP process. The tensile tests conducted at room temperature demonstrated a significant increase in strength with an increasing number of pressings, reaching 44.23, 53.19, and 56.7% for 1-pass, route A, and route R types 2-passes of the ECAP process, respectively. However, ductility, as indicated by elongation, gradually decreased after the first pressing. Electron backscatter diffraction was employed to reveal submicrometer grain sizes resulting from the ECAP process. The grain structure showed substantial improvement under route A and route R types at a 2-passes ECAP process. Wear tests conducted under loads of 10 and 25 N showed an increase in the coefficient of friction within the minimum wear loss intervals. Rockwell hardness also exhibited a significant increase of 119.3, 176.3, and 164.8% at 1-pass and 2-passes using routes R and A, respectively. As part of the evaluation, analytical models were computed using Python, and finite element simulations were performed using ABAQUS software. The results from analytical and finite element simulations demonstrated good agreement with the experimental data.

Enhancement of sintering and mechanical properties of alumina-rich Al2O3-MgO-CaO refractory composite by doping La2O3

Ceramics or refractories prepared in the Al2O3-rich corner of the Al2O3-MgO-CaO system show excellent high-temperature mechanical properties and chemical stability because of the presence of spinel (MgAl2O4) and calcium hexaluminate (CaAl12O19). However, the densification of these two crystals usually requires high firing temperatures due to their poor sinterability. To address this issue, La2O3-doped MgAl2O4-CaAl4O7-CaAl12O19 refractory composites were designed, and the influence of the doping level on the densification, microstructure, and mechanical properties of the composite was investigated. It was found that the doped La3+ was predominantly dissolved in the CA6 grains by replacing Ca2+, forming uniform solid solutions regardless of doping concentration. This reaction significantly accelerates ion diffusion and CA2 grain growth. Besides, it reduces the aspect ratio of CA6 crystals, weakening the negative effect of the elongated grains on mass transfer and sintering. As a result, the relative density increases from 79.5 % to 95.1 % after sintering at 1600 °C with doping only 0.5 wt% La2O3 into the composite, producing a uniform and dense microstructure with regular angular grains. The above effects result in a significant improvement in flexural strength and fracture toughness (increasing by 61 % and 57 %, respectively). Moreover, the La2O3-doped refractory composite achieves a decline of the high-temperature creep rate by one order of magnitude at 1600 °C.

Tailoring the additional content of short carbon fiber in the reduced graphene oxide-Cu self-lubricating composites for enhanced mechanical and tribological performance

The reduced graphene oxide-Cu self-lubricating composites with short carbon fiber fillers were fabricated by powders wet-mixing combined with hot-pressed sintering process. The impacts of short carbon fiber content on microstructure, mechanical and tribological performance of reduced graphene oxide-Cu composites were characterized. The reduced graphene oxide/carbon fiber hybrid fillers were randomly distributed in the sintered bulk compacts. The hybrid filled composites achieved enhancement in mechanical and tribological properties. With increasing carbon fiber content, hardness and compressive yield strength of the prepared composites were increased, and both friction coefficient and wear rate showed a constant decrease trend under different loads. Owing to the synergy effect of reduced graphene oxide/carbon fiber hybrid lubricant fillers during sliding together with the greatly enhanced hardness and yield strength, up to 0.6 wt% carbon fiber incorporation resulted a lowest friction coefficient and decreased wear rate. Randomly distributed reduced graphene oxide/carbon fiber hybrid fillers provided the lubrication to reduce friction and wear for Cu matrix.

Synergistic Enhancement of Mechanical Properties and Electrical Conductivity of Immiscible Bimetal: A Case Study on W–Cu

Immiscible bimetal systems, of which tungsten–copper (W–Cu) is a typical representative, have crucial applications in fields requiring both mechanical and physical properties. Nevertheless, it is a major challenge to determine how to give full play to the advantages of the two phases of the bimetal and achieve outstanding comprehensive properties. In this study, an ultrafine-grained W–Cu bimetal with spatially connected Cu and specific W islands was fabricated through a designed powder-mixing process and subsequent rapid low-temperature sintering. The prepared bimetal concurrently has a high yield strength, large plastic strain, and high electrical conductivity. The stress distribution and strain response of individual phases in different types of W–Cu bimetals under loading were quantified by means of a simulation. The high yield strength of the reported bimetal results from the microstructure refinement and high contiguity of the grains in the W islands, which enhance the contribution of W to the total plastic deformation of the bimetal. The high electrical conductivity is attributed to the increased mean free path of the Cu and the reduced proportion of phase boundaries due to the specific phase combination of W islands and Cu. This work provides new insight into modulating phase configuration in immiscible metallic composites to achieve high-level multi-objective properties.

Flexible and high-strength MXene/polyimide nanofiber aerogel membranes achieving infrared stealth through combined thermal control and low emissivity

The development of high-performance infrared stealth materials has been a long-standing goal for scientists. Despite their excellent performance, these materials are challenging to fabricate. In this work, a simple water immerse-stacking assembly process is employed to transform two-dimensional nanofiber membranes into three-dimensional aerogel membranes. Directional freezing from different directions induced varied orientations in the polyimide nanofibers (PINF), leading not only to unique anisotropic microstructures and thermal conductivities but also to synergistic enhancements in thermal insulation and mechanical properties. By vacuum-assisted filtration, MXene is embedded into the PINF membrane, resulting in a low emissivity of 0.283 and strong interlayer bonding of the MXene/PINF aerogel membrane without affecting the high and low-temperature resistance, the tensile strength, and the flexibility. Inspired by the art of origami, two types of MXene/PINF aerogel membrane bags are developed. When using one of the bags to cover an object at 130.2 °C, the thermal radiation temperature decreases to 28.9 °C. This study provides a promising approach for designing flexible, high-strength, and efficient infrared stealth composite materials, paving the way for further research and applications.

Enhancement of mechanical properties and machinability of aluminium composites by cupola slag reinforcements

AbstractRapid evolution in engineering and manufacturing demands light weight material with enhanced mechanical properties. Aluminium metal matrix composites with ceramic reinforcement particulates serve this demand due to their reduced density, improved strength and hardness along with higher resistance to wear and corrosion. However, the material cost and reduced machinability hinders the full potential of utilization. To overcome these challenges, in this work cupola slag, an industrial waste generated as by product of cast iron production, has been incorporated as reinforcement of aluminium composites using low cost stir casting method. The enhancement of material properties and machinability by cupola slag inclusion on base alloy has been investigated in detail. Moreover, introspection about the underlying mechanisms responsible for the improvement in material properties has been studied using detailed microstructure and fractographic analysis. The results show improvement of in material properties and machinability up to 7 wt.–% cupola slag inclusion, beyond which the reduced wettablity prohibits sound castings. The ultimate tensile strength and specific strength observed to be improved by 18.20 % and 33.23 % respectively for 7 wt.–% slag reinforced composites when compared with base alloy. This work can be a successful addition to the knowledge pool of ongoing research on low‐cost novel material with enhanced properties.

Synergistic Enhancement of Mechanical and Dielectric Properties in Transparent Polyimides by Regulating Hydrogen Bonding and Microbranched Cross-Linking Structure

Synergistic Enhancement of Mechanical and Dielectric Properties in Transparent Polyimides by Regulating Hydrogen Bonding and Microbranched Cross-Linking Structure

Synergistic Enhancement of Mechanical and Electrochemical Properties in Grafted Polymer/Oxide Hybrid Electrolytes.

Lithium metal batteries operated with high voltage cathodes are predestined for the realization of high energy storage systems, where solid polymer electrolytes offer a possibility to improve battery safety. Al2O3_PCL is introduced as promising hybrid electrolyte made from polycaprolactone (PCL) and Al2O3 nanoparticles that can be prepared in a one-pot synthesis as a random mixture of linear PCL and PCL-grafted Al2O3. Upon grafting, synergistic effects of mechanical stability and ionic conductivity are achieved. Due to the mechanical stability, manufacture of PCL-based membranes with a thickness of 50µm is feasible, yielding an ionic conductivity of 5·10-5S cm-1 at 60°C. The membrane exhibits an impressive performance of Li deposition in symmetric Li||Li cells, operating for 1200h at a constant and low overvoltage of 54mV and a current density of 0.2mA cm-2. NMC622|Al2O3_PCL|Li cells are cycled at rates of up to 1 C, achieving 140 cycles at >80% state of health. The straightforward synthesis and opportunity of upscaling as well as solvent-free polymerization render the Al2O3_PCL hybrid material as rather safe, potentially sustainable and affordable alternative to conventional polymer-based electrolytes.

Laser lap joining of R60702 zirconium alloy and 304 stainless steel utilizing CoNiTiV high entropy alloy

In this study, the laser lap welding of R60702 zirconium alloy and 304 stainless steel was successfully achieved by incorporating CoNiTiV high entropy alloy (HEA) interlayer. The addition of HEA interlayer altered elemental diffusion and prevented the formation of Zr-Fe intermetallic compounds. The maximum tensile and shear strength of the joint (998.4 N) is 2.5 times that of the sandwich joint without the HEA layer (392.1 N), with the displacement also increasing by 85 %. The inclusion of the intermediate HEA layer transforms the original brittle fracture mode into a tough-brittle mixed fracture mode. The elimination of Zr-Fe intermetallic compounds is the primary factor contributing to the enhancement of mechanical properties. The main phase composition includes α-Zr, Cr2Zr, CoTi2, Ni7Zr2 and Zr3Co phase.

Influence of nanofiller surface treatment on mechanical properties of pyrolyzed ceramic nanocomposites

The brittleness and limited plastic deformation of ceramics restrict their applications. In this work, the effects of pristine (CNTP), functionalized (CNTOH, CNTCOOH) and silanized MWCNTs on the mechanical properties of Silicon Carbide obtained by pyrolyzing polycarbosilane SMP-10 were studied. Functionalization with 3-glycidoxypropyltrimethoxy was analyzed through dispersion stability, zeta potential, and EDS analyses, revealing increased silicon content and colloidal stability in silanized MWCNTs. However, silanized MWCNTs led to reduced mechanical properties in composites, while untreated MWCNTs (CNTP, CNTOH, CNTCOOH), showed a substantial increase in modulus by 74.2 %, 86.9 %, and 30.5 %, respectively. The observed enhancement in mechanical properties exceeded the outcomes predicted by the rule of mixtures, suggesting notable morphological changes induced by MWCNTs. Potential underlying factors including toughening mechanisms and changes in porosity were evaluated and discussed in depth. Composites with untreated MWCNTs showed nearly a two-fold increase in fracture toughness. This work shows a streamlined approach for the development of ceramic nanocomposites (CNCs), achieving significant improvement in mechanical properties through pyrolysis, surpassing traditional methods reliant on densification processes. These findings demonstrate the substantial potential of CNCs, enhancing their suitability for advanced engineering applications.

Improved stabilization of loess soil using magnesium oxysulfate cement-based ecological composite binder

The technology of loess solidification plays a crucial role in addressing issues such as soil erosion, with the key material in this process being the loess stabilizer. To tackle the high energy consumption problem associated with traditional loess stabilizers primarily composed of Portland cement, this study employed a more ecological sustainable alternative by incorporating solid waste coal gangue and magnesium oxysulfate (MOS) cement as a binding agent for consolidating loess. The alterations in bulk density, porosity, mineral structure, and microstructure of the consolidated soil with different MOS content were systematically investigated and validated. The pore size of MOS-solidified loess decreased significantly to a range of 0.04–3.60 μm compared to 0.80–3.88 μm for pure loess. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and thermogravimetric (TG/DTG) analysis revealed that the addition of MOS binder generated hydrated magnesium silicate (M-S-H), Mg(OH)2, and a small amount of 5Mg(OH)2·MgSO4·7H2O phase which filled the gaps between soil particles and bonded them together effectively. When the proportion of MOS binder added reached 11 %, the compressive strength of stabilized loess after curing for 28 days increased up to 9.4 MPa. After immersion in water for 24 h, the strength only decreased by 5.3 %, with a softening coefficient of 94.7 %. The test results consistently indicate that the enhancement in mechanical properties can be attributed to the binding effect facilitated by MOS. The ecological composite binder based on coal gangue and MOS demonstrates great potential in the field of soil stabilization.

Role of scandium addition to microstructure, corrosion resistance, and mechanical properties of AA7085/ZrB2+Al2O3 composites

The effect of varying amounts of scandium (Sc) on the mechanical performance and corrosion resistance of aluminum alloy (AA7085) composites reinforced with Zirconium diboride (ZrB2) and Aluminum oxide (Al2O3) nanoparticles was investigated. The specimens were made using an in-situ process with varying amounts of Sc up to 0.5 wt%, and their microstructural behavior, corrosion, and mechanical properties were explored in detail. Phase structural analysis revealed the successful incorporation of ZrB2 and Al2O3 into the matrix through in-situ synthesis, ranging from 30 to 61.7 nm. In addition, HRTEM and XRD analysis displays the Al3Zr prominence observed with 0.1 wt% Sc content, transforming to Al3(Sc, Zr) in the 0.3 wt% Sc composite, and finally becoming Al3Sc with 0.5 wt% Sc. Corrosion analysis revealed that the 0.3 wt% Sc composite exhibited fine Al3(Sc, Zr) precipitate phases that enhanced corrosion properties. The Sc addition leads to a significant improvement in the mechanical properties of AA7085/ZrB2+Al2O3 composites. The ultimate tensile strength of 678 ± 5 MPa for 0.5 wt% Sc under the hot rolled and T6 aged condition was achieved. The optimum content of Sc in AA7085/ZrB2+Al2O3 composites has identified both corrosion and mechanical properties enhancement at 0.3 wt% and 0.5 wt%, respectively.

Comparative analysis of mechanical properties enhancement in SCM440 through similar and dissimilar material deposition using directed energy deposition method

The Directed Energy Deposition (DED) method, which utilizes metal powder and a high-powder laser directed at specific locations on a substrate, is employed across various fields for repairing and refurbishing existing parts. In this study, two types of multi-materials were fabricated by depositing materials similar in alloy composition, and dissimilar, respectively, on an SCM440 substrate using the DED method. Unlike similar material, depositing the dissimilar material resulted in a recrystallized fine microstructure in the interlayer region, which enhanced the tensile properties of the multi-layer specimens. The yield strength, tensile strength, and elongation of the multi-layer specimen with similar material were 562 MPa, 787 MPa, and 14%, respectively, while those of the specimen with dissimilar material were significantly higher at 934 MPa, 1016 MPa, and 30%. These results demonstrate that using dissimilar materials, rather than identical or similar compositions, can improve the tensile properties when repairing and refurbishing parts made of SCM440 material.

Enhancement of mechanical, barrier, and functional properties of chitosan film reinforced with glycerol, COS, and gallic acid for active food packaging

The demand for eco-friendly and natural food packaging materials has sparked considerable interest in the research and development of sustainable active packaging materials. In this study, a chitosan-based film was developed using glycerol as a plasticiser, chitooligosaccharide (COS) as an additive, and gallic acid as a cross-linking agent. The physical, barrier, mechanical, morphological, thermal, and functional properties of fabricated films were measured. The bio-composite film showed significantly lower moisture content (from 24.28 to 17.01%), water solubility (from 41.56% to 31.03%), water vapour permeability (14.63 to 9.79 × 10−9 gm−1s−1Pa−1), and light transmittance (from 63.67% to 21.71%) compared to neat chitosan film. Furthermore, the bio-composite film exhibited higher tensile strength (57.66 MPa) and elongation at break (88.76%), smooth microstructure, strong DPPH and ABTS radicals scavenging capacity, and good antimicrobial activity towards E. coli, L. innocua, and S. cerevisiae, and non-toxic to HaCaT cells indicating promising potential for use in sustainable active food packaging.

Enhancement of thermal and mechanical properties of PMMA nanocomposites by adding spark plug ceramic waste

In this research, poly methyl methacrylate (PMMA) resin was used as a base material and spark plug ceramic waste (CW) particles as a support material with different weight ratios (0%, 1%, 2%, 4%, 6%, 10%, 14%, and 20%) to study the thermal and mechanical properties through diffraction examination. FE-SEM surface structure images showed that the fracture surface of the (94% PMMA +6%CW) nanocomposite sample manifests a good distribution of particles at low and high levels. The result showed that the thermal conductivity (K) slightly increased until it reached the maximum value (0.6 watt/m.ºC) at the ratio (86%PMMA +14%CW). For the impact strength, it was noticed that the impact strength of PMMA increases with the increased weight ratios (1, 2, 4, 6, 10, 14, and 20%) of fine powder of ceramic waste compared with pure PMMA to reach the maximum value (6.02 kJ/mm2) at the sample (94% PMMA +6%CW) under L.C. Moreover, after 30 days of submersion in water, the PMMA reinforced with ceramic waste particles had enhanced impact strength. The shore D-number readings for all of the samples showed an increase as a result of the findings of nanocomposite compared with PMMA pure, where the sample (94% PMMA+6%CM) attained the greatest shore D numbers (87 H.NO). The compressive strength at the weight percentage (99% PMMA + 1% CW) was somewhat reduced. Then the compressive strength increased till it reached its maximum value (29.94 MPa) at the weight percentage (94% PMMA + 6% CW).

Inhibition of interfacial reaction and enhancement of mechanical properties of CF/Al composite

The properties of carbon fiber-reinforced aluminum matrix (CF/Al) composite for aerospace applications are often limited by interfacial reactions. In this study, chemical vapor deposition (CVD) was applied to prepare pyrolytic carbon (PyC) coatings with different thicknesses on CF surfaces to reduce the C/Al interfacial reaction and improve the mechanical properties. Liquid-solid infiltration extrusion (LSIE) was used to prepare CF@PyC/Al composite, and the effects of coating thickness on the interfacial microstructure, tensile properties and fracture behavior were investigated. The experimental results showed that the PyC coating enhanced the oxidation resistance of CF, but the toughness and tensile strength of the CF decreased. The coating effectively suppressed the generation of Al4C3 and provided a better quality interface for the composite. Compared with the uncoated CF/Al composite, the tensile strength of the CF@PyC/Al composite was enhanced by 35% at a coating thickness of about 0.23 μm. In addition, the strength and modulus of the coated material behaved more stably at different layup angles, whereas the uncoated material was more sensitive to angle changes. These performance enhancements are mainly attributed to the effective hindrance of Al4C3 production by the coating, which enhances the crack deflection frequency and enhances the energy absorption capacity.

Direct aging treatment of TiN modified Al–Mn–Sc alloy processed by laser powder bed fusion: On the microstructure evolution and mechanical property enhancement

In this study, the TiN nanoparticles modified Al–Mn-Sc composite and Al–Mn-Sc alloy have been fabricated by the laser powder bed fusion (LPBF). The microstructure, mechanical properties and strengthening mechanisms of these materials were discussed in details for both the as-built and artificial aged conditions. The results showed that the aged Al–Mn-Sc/TiN composite exhibits homogeneous nucleation with equiaxed grains ranging from 0.81 μm to 1.30 μm. After direct aging treatment of 300 °C, there are a volume fraction of secondary L12-Al3(Ti, Sc, Zr) nanoparticles precipitated in the composite sample, contributing to an ultra-high fracture strength of 701 ± 16 MPa. The increment in strength brought by TiN mainly comes from fine grains and high volume fraction of L12-Al3(Ti, Sc, Zr) nanoprecipitates. The fracture behaviors suggest that the uniform distribution of reinforced particles and less amount of micro pores can improve the strength and ductility of LPBF particle reinforced aluminum matrix composites.