The figure shows the atomistic configurations of TiN/Al workpiece with different surface orientations of the TiN layer (a) and the Al layer (b,c).
Display omitted
•Effect of layer orientation and ...thickness on mechanical properties of TiN/Al is studied.•The TiN(111)/Al(111) sample with Ti-face has the largest loading force and hardness.•The sink-in in indents appears for samples with the change in surface orientations.•High stress and strain are concentrated at the interface and around the indenter.•The interface acts as a barrier against deformation spread to the inside of sample.
This paper investigates the influence of the surface orientation of TiN and Al layers, as well as TiN layer thickness on the deformation behavior and mechanical characteristic of TiN/Al bilayer composites under the nanoindentation process through molecular dynamics (MD) simulation. The result shows that the TiN(111)/Al(111) workpiece with Ti-face has the greatest loading force and hardness, indicating that the strength of this specimen is improved better than other surface orientations, and the increase in TiN layer thickness leads to increase the loading force and hardness. However, defects such as dislocation and phase transformation appear also more in the TiN(111)/Al(111) workpiece with Ti-face, while the phase transformation and the number of dislocation in the Al layer are clearly decreased as increasing the TiN layer thickness. The surface morphology reveals that the sink-in phenomenon in indents has occurred in all samples with the change of TiN/Al surface orientations. Besides, the indents appear the sink-in for TiN layer thickness from 10 Å to 30 Å, and the pile-up is present in the indentation with TiN thicknesses of 50 Å and 70 Å. The atomic zone in the high stress–strain state is focused on the interface and around the indenter in all samples, and the interface acts as a barrier against the spread of stress and strain into the substrate interior. Furthermore, the atomic area in the high-temperature state is concentrated surrounding the indenter due to the friction between the substrate and indenter, and the deformation process of material from elastic to plastic causes the heat increase in the substrate
The displacement vector of Cu-Zr atoms under imprinting process after completion unloading stage at temperature of 300 K for different alloy compositions.
Display omitted
•The imprinting force and ...the STZs increase as increasing angle of the punch.•The residual stress rises up in the loading, reduces in the unloading as a larger speed.•The atoms move more disorderly, the RDF peak decreases as increasing temperature.•The atoms movement is denser, the residual stress increases as greater Cu content.•The Cu-Zr MGs formability can be improved by increasing Cu content, and velocity.
Molecular dynamics simulations are employed to study mechanistic characteristics of Cu-Zr metallic glasses films during the imprinting process. The influences of punch geometry, loading velocity, temperature, and alloy composition are exhaustively analyzed in terms of imprinting force, deformation characteristic, residual stress, displacement vector, radial distribution function, and elastic recovery ratio. The results show that the imprinting force and the shear transformation zones (STZs) of the Cu50Zr50 MGs films increase, while the residual stress has slightly changed with increasing angle of the punch. In the case of different imprinting velocities, the imprinting force increases. The residual stress also increases in the loading stage; however, it decreases in the unloading stage. The imprinting force, residual stress, highest peak of the radial distribution function (RDF) decrease and movement of atoms become irregular as increasing of temperature. As increasing Cu proportion, the imprinting force increases, the density of atom movement and residual stress increases, while the highest peak of the RDF decreases. The formality of the Cu-Zr MGs films can be improved by increasing Cu proportion and loading velocity, decreasing temperature due to lower average elastic recovery ratio. The imprinting force values are in the range of 100–185 nN, the residual stress values of the loading stage are from 0.44 to 0.82 GPa and the residual stress values of the unloading stage are from 0.4 to 0.9 GPa, the elastic recovery ratio are in the range of 0.17–20.26%.
The figure shows the atomistic configurations of mono-crystal AlCrCuFeNi2 high-entropy alloy samples with a pre-void (a1) and a pre-inclusion (b1) at the strain value of 0.2: von Mises shear strain ...(a2 and b2), atomic phase (a3 and b3).
Display omitted
•The mechanical parameters are decreased under increasing the void size and reducing the strain rate.•There exists a critical value of the mechanical parameters at the tension of sample with an inclusion size of 15 Å.•The deformation behavior reveals that the void and inclusion are the main cause of initial strain.•The HCP phase of inclusion exhibits relatively unstable, demonstrated by a rapid phase transformation of inclusion.
The effects of various void sizes, inclusion sizes, and strain rates on the mechanical response, deformation behavior, and failure mechanism of AlCrCuFeNi2 high-entropy alloy samples with a pre-void/inclusion under the tension are investigated via the molecular dynamics. The results reveal that there exists a critical value of mechanical parameters such as the tensile strength and Young’s modulus in the tension of sample with an inclusion size of 15 Å, where the mechanistic parameters are changed. Meanwhile, the mechanical parameters decrease under increasing the void size and reducing the strain rate. The deformation behavior discloses that the void and inclusion are the principal cause of initial strain, and the shear bands are propagated inside the workpiece along the direction of an angle of 45° related to the tensile axis. The transformation from the FCC phase to other structures such as HCP and amorphous has occurred during deformation. Also, the HCP phase of inclusion shows relatively unstable, which is demonstrated by a rapid phase transformation of inclusion under a small strain. Finally, the dislocation evolution mechanism exhibits that it begins to nucleate around the void and inclusion, and the dislocations are then moved to free surfaces with increased strain.
Hydroxypropyl methylcellulose (HPMC) is a common hydrophilic and biodegradable polymer that can form films. This study incorporated aluminum nanoadditives as an enhancement reagent into a HPMC ...matrix. Mechanical properties of nanocompoistes, including the tensile strength and the elastic modulus, were analyzed with a nano-tensile tester. The incorporation of additives in HPMC films significantly enhances their mechanical and film barrier properties. Evidence of bonding between the additive and matrix was observed by Fourier-transform infrared spectrometer analysis. The additives occupy the spaces in the pores of the matrix, which increases the tendency of the pore to collapse and improves the chemical bonding between the base material and the additives. The incorporation of excess additives decreases the tensile strength due to ineffective collisions between the additives and the matrix. The wear test proves that the addition of nano-additives can improve the tribology performance of the HPMC composite while reducing the wear volume and the friction. Bonding between the nanoadditives and the matrix does not help release the nanoadditives into the wear interface as a third-body layer. The main reason to enhance the tribology performance is that the nanoadditives improve the load-capacity of the composite coating. This hybrid composite can be useful in many sustainability applications.
Abstract
High-entropy alloys consisting of CoCrFeNiAl as the major elements and 2–5 at% Mn as the minor element were prepared using a vacuum arc melting method. The crystalline structures of the ...prepared alloys were identified by x-ray diffraction. Moreover, the mechanical properties of the alloys were examined under quasi-static (10
−1
, 10
−2
and 10
−3
s
−1
) and dynamic (3000, 4000, and 5000 s
−1
) loading conditions using a universal testing machine and split-Hopkinson pressure bar system, respectively. The experimental results showed that, for all of the HEA alloys, the flow stress and strain rate sensitivity coefficient increased with increasing strain rate. Among all the alloys, that with 3 at% Mn exhibited the best mechanical properties. A significant loss in plasticity was observed as the Mn content increased to 5 at%. The scanning electron microscope observations showed that the favorable mechanical properties of the alloy with 3 at% Mn were the result of a compact dimple structure, which enhanced the toughness. The HEA with 5 at% Mn showed the best electrochemical corrosion resistance among all the alloys due to the formation of dendritic structures at the grain boundaries.
Synthetic polymers are the most commonly used polymers in daily life. Therefore, it is necessary to develop environmentally friendly polymers. Hydroxypropyl methylcellulose (HPMC) is a potential ...candidate for a biopolymer, owing to its unique properties. However, HPMC biopolymers have some disadvantages compared to synthetic polymers. In this study, the mechanical properties and tribological performance of MoS2 additive-enhanced cellulose matrix biocomposites were investigated in order to improve the properties of HPMC. MoS2 was incorporated into the HPMC matrix as a strengthening additive. The mechanical properties, bonding, and water vapor permeability of the composites were analyzed. The mechanical and vapor barrier properties of the HPMC films were significantly enhanced. The ultimate tensile strength and Young’s modulus of the composite films increased with the addition of up to 1 wt% MoS2. The water vapor permeability of HPMC films reduced when additives were incorporated. The wear test proves that the MoS2 additives can improve the tribological performance of the HPMC composite while reducing the friction coefficient. The main reason for enhanced tribological performance is the improvement in load capacity of the composite coating by the MoS2 additive. This MoS2/HPMC biocomposite can be used in food packaging.
Display omitted
•Additionally input the ionized gaseous water molecules into the gasoline engine by using the corona discharge.•The brake-specific fuel consumption (BSFC) was improved up to 3.0% with ...the ionized gaseous water molecules at 1000 Hz and 30 V corona discharge.•Ionized gaseous water molecules were advantageous in the reduction of CO, but increased NOx and HC.•The corona’s voltage and frequency increase in systems that increase horsepower, HC, NOx, and exhaust temperature and reduce BSFC and CO.
Among various air pollution issues, exhaust emissions from internal combustion engines have become one of society’s primary concerns. This study analyzed the water system and plasma system installed on the intake manifold to investigate the effects of additional substances produced by the electrolysis of saturated gaseous water molecules on engine performance and exhaust emissions. The results indicate that electrolyzing gaseous water molecules produce hydrogen and oxygen at different voltages and frequencies of the corona, which affects the power efficiency and the brake-specific fuel consumption (BSFC) of internal combustion engines. Moreover, it affects the concentration of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The result shows that engine power increased by 2.5%, BSFC decreased by 3%, and CO decreased by 9%. However, the result indicates that HC increased by 29%, and NOx increased by 21%. In conclusion, electrolyzing saturated gaseous water molecules in a non-thermal plasma improves engine performance but increases the concentration of HC and NOx. However, the changes in performance and exhaust emissions are only noticeable at higher ignition frequencies of the non-thermal plasma, and the performance changes at lower frequencies are like only using the water system.
PDF
