Improvement Of Mechanical Properties Research Articles

Development of parametric window and optimization of process parameters to predict bead profile in magnetically controlled gas tungsten arc welding

A novel methodology has been proposed to tame the arc shape by adopting an external magnetic field, resulting weld profile as required. The co-axial magnetic field developed by specially designed electromagnets is superimposed on the welding arc. It was found that 0-0-S-N configuration provided more penetration than conventional gas tungsten arc welding. A parametric window has been developed for the selected configuration to obtain the desired bead geometry. The experiments were performed using process parameters as suggested by the design matrix, developed using response surface method technique. Mathematical models were evolved from experimental data for penetration and bead width. The evolved model for penetration is adequate up to 99.72% confidence level and for bead width is 99.98% confidence level. The effects of process parameters have been presented in a graphical manner for better understanding. The penetration achieved with the magnetically controlled GTAW process is 3.92 mm, which is 30% more than that achieved with conventional GTAW. The bead width increases initially, up to a certain limit, and then reduces with an increase in excitation current. Further, the experiments have been conducted on the optimized parameters for the validation of models. The refined grains were obtained due to magnetic stirring of the molten pool, which is desirable for improvement in mechanical properties of welds. The average grain size was reduced from 42.55 to 31.03 µm. The improved microstructure containing more amount of acicular ferrite was obtained with magnetically controlled arc.

Effects of multi-axial compression and double-step aging on the microstructure and mechanical properties of Al alloy 7075

This study investigates the combined effect of severe plastic deformation via multi-axial compression (MAC) and subsequent double-step aging on the microstructure and mechanical properties of annealed 7075 Al alloy. Three distinct processes were employed: (1) double-step aging on the annealed sample, (2) double-step aging on the six-MAC pass processed sample, and (3) double-step aging without solutionization on the six-MAC pass sample. Process (2) yielded the most significant improvements in mechanical properties. Compared to the annealed sample, the six-MAC pass, double-step aged sample exhibited an average ultimate tensile strength increase of 134% and an average Vickers micro-hardness (HV) increase of 209%. This superior performance is likely attributable to the synergistic effect of grain refinement induced by MAC and precipitate hardening achieved through double-step aging. A comprehensive analysis of microstructure evolution, mechanical properties, fractography, and the relationship between them was conducted for all three processes. This in-depth examination provided valuable insights into the mechanisms governing the observed property enhancements, particularly in process (2). Additionally, a variety of characterization techniques were employed to comprehensively evaluate the material's mechanical and microstructural characteristics.

Synergistic Improvement of Mechanical and Corrosion Properties of Mg-9.1Y-1.8Zn Alloys by Hot Extrusion

Synergistic Improvement of Mechanical and Corrosion Properties of Mg-9.1Y-1.8Zn Alloys by Hot Extrusion

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

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 1 wt% e-MXene@Ag1.0 decreased by 30.3%, 33.3%, 18.2%, and 20.1% respectively. 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’.

Optimizing the surface quality of heat-treated 2Cr13 stainless steel via electrochemical machining

The improvement of mechanical properties and surface quality was of great significance for materials. In this study, 2Cr13 stainless steel was subjected to the quenching and tempering treatment. The electrochemical machining approach was adopted for surface treatment. The results showed that the quenching and tempering treatment improved the Vickers microhardness of 2Cr13 stainless steel. The enhancement of microhardness was facilitated by the formation of tempered sorbite and grain refinement. Electrochemical machining provided high quality surfaces. The heat-treated workpice had more advantages in electrochemical machining efficiency. The polarization curves proved a downward shift of the self-corrosion potential for the heat-treated 2Cr13 stainless steel, which was strongly related to the electrochemical behavior. A mechanism model for promoting anode electrochemical dissolution was proposed.

Influence of Hydroxyapatite Content on Physical and Rheological Properties of Chitosan-based Scaffold

Chitosan-based scaffolds offer significant potential in tissue engineering and regenerative medicine. Whilst exhibiting great bio-regenerative and biocompatible properties, their mechanical properties remain quite poor. The presented research is focused on the modification of macroporous chitosan scaffolds with various amounts of bioactive ceramics (hydroxyapatite) and its influence on the physical and rheological properties of the composite scaffold. Chitosan/hydroxyapatite composite scaffolds with a highly porous microstructure have been prepared by suspending hydroxyapatite (HAp) particles into the chitosan matrix. According to SEM imaging, homogeneous dispersion of the inorganic phase in a chemically-crosslinked chitosan matrix had been achieved. The obtained composite scaffolds exhibited lower swelling capacity with respect to pure chitosan after 24 h of incubation in Hanks’ balanced salt solution. Rheological measurements show an increase in storage and loss modulus indicating an improvement in mechanical properties under shear stress. Furthermore, no significant change in loss factor (tanδ) was observed indicating no change in composite viscoelastic properties with an increase in HAp content.

Optimization, Sodium Hydroxide and Plantain Fibres: Mechanical Properties of Unsaturated Polyester Composites for Transtibial Prosthetic Socket

Low mechanical behaviors of natural fibres in the reinforcement of polymer composites have remain an issue of concern. This study is aimed at investigating the effect of NaOH treatment on the mechanical properties of plantain fiber for the transtibial prosthetic sockets made of polyester resin. Plantain fiber was extracted from the plantain bast using water retting techniques. The fibres were modified using alkaline treatment method of 5 – 25% for variable time of 30 to 150 minutes. It was optimized using 3-level Factorial design (3-LCD) of response surface methodology based on tensile properties of treated fibres. The polyester composites of plantain and glass fibers were prepared using hand-layup techniques. Instron Universal testing machine-3369 model was used to determine the tensile and impact properties of fibers and polyester composites. Rockwell hardness tester-RBHT/S-39 model was used to determine the hardness property. The optimum process conditions of 5 % NaOH for 119 minutes improved plantain fiber tensile strength, modulus, strain, energy, and extension by improved by 102.03, 208.07, 9.70, 210.52 and 205.73 %, respectively. The ultimate tensile strength and modulus was obtained at 10 and 12.5% fiber loading. The hardness and impact strength of NaOH modified unsaturated polyester composites was marginally more than 3.51 and 10.69% of glass fiber reinforced unsaturated composites, respectively, at 12.5% fiber loading. FTIR analysis revealed the improvement in mechanical properties. Thus, NaOH modified plantain fiber unsaturated polyester composites serves as a better alternative for making transtibial prosthetic socket.

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.

Antifouling and antimicrobial 3D printed small household appliances with incorporation of zwitterions and quaternary ammonium compounds

Nowadays, small household appliances had revolutionized the way we live and work with unparalleled innovation and performance, but the bacterial colonization of the appliance surfaces was a widespread phenomenon with consequences on human health and well-being. In this work, a spectrum of composite resins with addition of different ratios of sulfobetaine methacrylate (SBMA) and 12-methacryloyloxydodecylpyridinium bromide (MDPB) were prepared by photocuring 3D printing technology for improving their antifouling and antimicrobial properties. A remarkable improvement in mechanical property was observed as a result of the electrostatic attraction between SBMA, MDPB and polyurethane. The composite resins exhibited a relatively hydrophilic surface because of the high hydration capacity of zwitterionic SBMA, which enabled effective suppression of protein adsorption and bacterial adhesion, resulting in excellent antifouling property. Meanwhile, the antimicrobial property of the composite resins against both S. aureus (Gram-positive bacteria) and E. coli (Gram-negative bacteria) was significantly improved in the presence of MDPB, and the resins with 20% MDPB showed the best antimicrobial property, with a reduction rate of 98.3% and 97.1% against S. aureus and E. coli, respectively. Not only that, all composite resins persevered low cytotoxicity and good biocompatibility. More importantly, a series of children's nebulizers with enhanced protein adsorption resistance, reduced bacterial fouling and sustained biocompatibility were fabricated by photocuring 3D printing technology using the composite resins, confirming the success of antifouling and antimicrobial composite resin strategy in small household appliances.

Damping and mechanical behavior of graphene nanoplatelets reinforced Al-30Zn alloy matrix bioinspired laminated composites by two steps flake powder metallurgy

Damping and mechanical properties are often incompatible in metallic materials. In this paper, bio-inspired laminated graphene nanoplatelets (GNPs) reinforced Al-30Zn alloy matrix composites with an outstanding combination of damping-mechanical properties are prepared using a flake powder metallurgy (FPM) process. The increased grain/phase boundary owing to grain refinement improves the intrinsic damping properties of the composites, while the lamellar grains promote the oriented alignment and crack deflection of GNPs. The multilayered GNPs with large specific surface area experienced repeated stretching and compression during cyclic bending deformation, leading to intense interfacial frictional slip, and GNPs' high intrinsic thermal conductivity also helped to dissipate heat quickly, which promoted mechanical energy dissipation. The improvement in mechanical properties is mainly attributed to grain refinement, the load transfer effect of GNPs and their interaction with dislocations. The Al-30Zn-0.5GNPs composites showed the best combination of damping properties and mechanical properties.

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.

Tough double-network hydrogels with excellent frictional properties based on the in-suit inhibition strategy for biomedical applications

Osteoarthritis (OA) is one of the most common joint disorders all over the world and hydrogels could be an effective tool to solve this problem. In this work, we explore the mechanism of tribology properties of double-network hydrogel (DN hydrogel) under effect of free radical polymerization inhibitors. Fe3+ is added to the DN hydrogel as highly efficient and easily adjustable inhibitor, and the friction coefficient can be reduced to 0.0038 by adjusting the concentration. Even after 6 hours of continuous tribological testing, the DN hydrogel remains a surprising sustained superlubricity. Furthermore, the strength of the hydrogel can reach 2.36 MPa, which is 20 times higher than that of the single-network hydrogel (SN hydrogel). The introduction of the inhibitor reduces covalent crosslinking that enables the hydrogel to form a sparser mesh structure conducive to the reduction of the friction coefficient, especially the additional physical cross-linking delivered from the electrostatic interaction between Fe3+ and carboxyl groups increases strength. The optimum concentration of Fe3+ is explored to achieve the synergetic improvement of lubricative and mechanical properties. This work opens innovative technology routes for developing superlubricious and tough hydrogels, which is a brighter future for artificial cartilage applications.

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.

Comparative studies of different solutes effects on microstructure and comprehensive performance of coherent precipitation-strengthened Cu–Ni–Al alloys

Multi-componentization can further improve the heating resistance of Cu-Ni-Al alloys, enabling them to withstand more demanding situations. Unfortunately, the limited researches have been done on the wear and corrosion resistance of the heat-resistant Cu-Ni-Al alloys, resulting in the lack of relevant evidence in the practical application. In this work, a comparative study of differential types of trace element, Si (the stronger enthalpy interaction element), Sn (the weaker enthalpy interaction element) Cr or Zr (grain boundary strengthening element), effects on microstructure, wear and corrosion resistance will be done, Furthermore, the effect of different trace elements on the surface electron work function and electrochemical behavior of Cu-Ni-Al alloys is reflected by SPM surface potential model. The results indicate that the precipitation of dual nano-phase and accelerated precipitation of γ' phase can be realized through the addition of Si, Sn, Cr and Zr, in which the value of δγ-γ′ increase sharply after adding Si and it is not conducive to the preservation of cuboidal γ' phase. The addition of Si, Cr and Zr can improve electron work function distribution and mechanical property, wear, and corrosion resistance of the alloys, in which Si is more conducive to the improvement of wear resistance and mechanical properties of the alloy, while the alloy with Cr and Zr shows the excellent corrosion resistance. The addition of Sn will weaken the enthalpy interaction of the alloy system, reduce the electron work function of the alloy, and have adverse effects on the wear and corrosion resistance of the alloy.

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.