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Physical modeling of the nanoindentation problem. The indenter is analytically rigid as modeled in LAMMPS
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Nanoindentation is a powerful tool capable of providing fundamental insights of material elastic and plastic response at the nanoscale. Alloys at nanoscale are particularly interesting as the local heterogeneity and deformation mechanism revealed by atomistic study offers a better way to understand hardening mechanism to build a stronger material....
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Citations
... However, the mechanical properties of h-Al 2 Cu are low, as reported by Wang et al. [39], who found that it is brittle at ambient temperature due to elevated lattice friction stress [40,41]. Additionally, the mechanical properties of as-cast Al-Al 2 Cu eutectic alloys depend on interlamellar spacing, with fracture strain and strength increasing as the interlamellar spacing decreases [40,[42][43][44][45][46][47][48]. Although the presence of a-AlFeSi, a-Al (FeMn) Si, and eutectic silicon can enhance the mechanical properties of Al-alloys, the Cu-enriched intermetallic phase is predominant, resulting in increased ductility but lower mechanical properties compared to Set 2 and Set 3. The size of the intermetallic phase formed is in the micron range, with Al-Al2Cu-Si at 7 µm, h-Al 2 Cu at 10, and 11 µm, respectively, which is consistent with the findings of Lombardi et al. [49,50]. ...
The present research focuses on the recycling of various aluminium scraps that contain significant levels of silicon, iron, manganese, and copper to create a new aluminium alloy with superior properties. The alloy was designed to exhibit high extrudability and mechanical properties. The alloy was extruded at a low temperature of 430 °C, resulting in a good yield and form free of extrusion flaws. The produced alloy was characterized in three sets: Set 1 without aging (0 h), Set 2. with different aging times (3, 4, and 5 h) at 185 °C, and Set 3. with heat treatment and different aging times (3 h., 4 h., and 5 h.). The mechanical, electrical, and microstructural properties of each set were investigated. The samples in Set 1. had poor mechanical properties but high ductility due to the presence of Cu-enriched intermetallic as the dominant phase. Set 2 samples had the best mechanical properties while preserving high ductility, which was due to the synergy between α-Al (FeMn) Si, Cu-enriched intermetallic, spheroidal AlCuMgSi, and modified silicon particles. Set 3. samples underwent heat treatment at an elevated temperature (530 °C for 3 h) with rapid quenching, then aged for varying times and quenched rapidly, this led to the dissolution of the Cu-enriched intermetallic except for the AlMgCu phase with (Al96Mg3Cu1 and Al94Mg5Cu1, at. %), and the dominant phase was α-Al (FeMn) Si phase, which improved mechanical characteristics. Overall, the ASH01 alloy produced in Set 2 conditions is a promising alloy with strong mechanical characteristics and ductility as a recycled Al-scrap alloy.
... The increased strength results in the seriously decreased plasticity and machinability with the addition of the particles into the matrix alloys. The ductility is maintained or increased of the AMCs when the particles decrease to nano-size [17][18][19][20]. However, the nano-sized particles are difficult to distribute homogeneously in Al-matrix [21][22][23][24]. ...
The microstructure and properties of Al-matrix composites are directly determined by ceramic particles in the matrix, such as synthetic methods, morphologies, sizes, interface, etc., especially the distribution of particles. Hereinto, Al-matrix nanocomposites, which show brilliant, comprehensive properties, have been widely studied. How to give full play to its advantages in further applications in automotive and aerospace areas has attracted considerable attention from researchers. In this review, current development on the pre-distribution of reinforcement particles and deformation processes and microstructure, mechanical properties of Al-matrix composites reinforced with in-situ and ex-situ nanoparticles will be addressed. In addition, the corresponding development prospects and challenges of nanoparticles reinforced Al-matrix composites fabricated by a combination of pre-distribution and deformation were also summarised.
... Among the pure elements, Al is one of the best conductors of electricity and heat. It is one of the elements with a very soft structure, which makes it difficult to use it in engineering fields that require high mechanical strength [2]. Although Al is approximately three times lighter than iron. ...
... For example, Al alloys are used in our daily life, in modern construction, automotive, aviation, energy, food, and other industries, even in many technological devices that we always keep with us [3][4][5]. Because of all these properties, there are many studies in the literature on Al and its alloys [2,[6][7][8][9]. Unlike other studies, we focused on the melting process of Al under various external pressures (P=0, 5, 10, 15, and 20 GPa), and this process has been carried out with molecular dynamics (MD) simulations, which have many advantages. ...
Molecular dynamics simulations are based on investigating various physical properties of pure aluminum during the heating process under different pressures (between 0-20 GPa). In all simulations, we preferred the very popular embedded atom method potential for metals and their alloys to describe the interactions between aluminum atoms in the system. The melting point and atomic structure of aluminum under pressure have been studied using several structural techniques such as pair distribution function, structure factor, and pair analysis. In this study, the results obtained for the system under 0 GPa pressure are compared and discussed with appropriate experimental or other results previously reported. The findings show a good agreement between our results and the experimental results. The increased pressure has been caused the system to melt at higher temperatures. We believe that the present results will provide useful information about aluminum under different conditions such as temperature and pressure and contribute to the literature.
... Molecular dynamics (MD) simulations can be regarded as a powerful tool to investigate and understand the mechanical, thermal, electrical properties, and fracture mechanisms of the heterostructures in nanoscale. For a variety of research, the results obtained from MD simulations have been well supported by the results of experiments, as well as numerical models [25]. Elder et al. explored the mechanical characteristics of bi-and tri-layer heterostructures containing graphene and MoS 2 , where MoS 2 is supported or capsulated by graphene and compared with their monolayers and homogeneous bilayers using MD simulations [26]. ...
The heterostructures synthesized by vertically stacking two-dimensional (2D) materials exhibit appealing and sophisticated features and functions that are typically missing in single-layer 2D materials. In our present study, the chirality and temperature-dependent mechanical characteristics and fracture process of graphene/h-WS2/graphene (GWG) vertical heterostructure in both armchair and zigzag loading directions are investigated utilizing molecular dynamics (MD) simulations. Our findings reveal that vertically sandwiching h-WS2 between two graphene layers significantly improves the h-WS2 monolayer's mechanical characteristics (Young's modulus and ultimate stress). Young's moduli of the heterostructure are higher than that predicted by the rule of mixture (ROM), especially at high temperatures. This points out a significant enhancement of mechanical properties due to the vertical stacking and strong interlayer interaction of graphene and WS2 layers. Moreover, we have discovered that while armchair loading causes the fracture to begin in the graphene layers, zigzag loading causes the crack to begin in either the WS2 layer or the graphene layers. Finally, this study illustrates an intriguing and thorough characterization of the GWG vertical heterostructures' mechanical properties and fracture mechanisms, as well as their temperature dependence and directional anisotropy, allowing for efficient and versatile application of the material in a variety of fields.
The grain boundaries and dislocations play an important role in understanding the deformation behavior in polycrystalline materials. In this paper, the deformation mechanism of Cu, Ni, and equimolar Cu-Ni alloy was investigated using molecular dynamic simulation. The interaction between dislocations and grain boundary motion during the deformation was monitored using the dislocation extraction algorithm. Moreover, the effect of stacking fault formation and atomic band structure on the deformation behavior was discussed. Results indicate that dislocations nucleate around the grain boundary in copper, the deformation in nickel changes from planar slip bands to wavy bands, and high density of dislocation accumulation as well as numerous kink and jog formations were observed for the equimolar Cu-Ni alloy. The highest density of the Shockley dislocation and stacking faults was formed in the equimolar Cu-Ni alloy which results in the appearance of a huge gliding stage in the stress–strain curve. The grain boundaries act as a sinking source for vacancy annihilation in Ni and Cu; however, this effect was not observed in an equimolar Cu-Ni alloy. Finally, radial distribution function was used to evaluate atom segregation in grain boundaries.
Fe–Cr–Al alloy is one of the candidate materials for reactor fuel cladding due to excellent high-temperature oxidation resistance; however, it has significant irradiation embrittlement and hardening. To understand the effect of Cr and Al and the defects (point defects, clusters, and nanocracks) produced from radiation damage on the mechanical properties, the uniaxial tensile property of single-crystal Fe–Cr–Al is investigated. The results show that, due to the presence of Cr and Al, the phase transformation from body-centered-cubic to face-centered-cubic is impeded and the formation of defects and amorphous structures is promoted, leading to the reduction of Young’s modulus and the ultimate tensile stress. Interstitials are the main factor in Frenkel pairs contributing to the reduction of mechanical properties due to the high shear stress and lattice distortion. The collapse of the nanocrack causes the increase of Young’s modulus and the decrease of the ultimate tensile strength.Graphical abstract
Effects of strain rates on mechanical behaviors of nano-multilayered aluminum 5052 alloys are explored via molecular dynamics simulations. Yield strength and ultimate tensile strength increase with an increase in strain rates. The increase of the yield stress with the strain rate is caused by the delay in the onset of dislocation propagation. In addition, the strain rate sensitivity and the yield stress activation volume significantly depend on strain rate. Under tensile loading, the pristine face-centered cubic structure of the alloy successively transforms to a hexagonal close-packed structure through the intermediate body-centered cubic structure during plastic deformation processes, regardless of strain rates. Dislocation density and volume fraction of phase significantly depend on strain rate. In addition, discussions on the formation, movement, and interaction of dislocations under low and high strain rates are presented.
The interaction between cracks, as well as their propagation, in single-crystal aluminum was simulated at the atomic scale by molecular dynamics method and modified embedded atom method. Further, the effects of the distance between two cracks and the difference of crack size on crack propagation and mechanical properties were comprehensively investigated. The results demonstrated that multi-crack propagation in aluminum is a quite complex process, which is accompanied by micro-crack growth, merging, stress shielding, and the crossing of slip bands. During crack propagation, there are interactions between cracks. Such interactions inhibit the phase transition, dislocation and slip bands at the crack tip, and also affect the direction of crack propagation. The intensity of the interaction between two cracks decreases with the increase of the distance between them and increases with increasing crack size. Moreover, the strength limit of aluminum decreases with the increase of the distance between cracks and the difference in their size.
