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This study compares the tensile properties of single-phase and dual-phase polycrystalline FeNiAl alloys using molecular dynamics (MD) simulation. The findings reveal that dual-phase polycrystalline materials, incorporating both B2-NiAl and face-centered cubic (FCC)-Fe phases, exhibit significantly superior strength and strain hardening compared to their single-phase FCC-FeNiAl counterparts. The back stress and Bauschinger effect emerge as pivotal factors in strengthening and strain hardening during the tensile deformation of dual-phase polycrystalline materials. In single-phase polycrystalline materials, grain plastic deformation is uniform, primarily driven by Shockley partial dislocation b = 1 6 < 121 > . Additionally, deformation twinning is observed with increasing strain. Conversely, in dual-phase polycrystalline materials, non-uniform plastic deformation occurs because of differences in crystal structure between the two phases. Plastic deformation predominantly takes place in the soft domain FCC-Fe grains, while dislocations encounter hindrance from the hard domain B2-NiAl grains, leading to the generation of back stress. The direction of dislocation movement opposes the back stress, further impeding plastic deformation and enhancing material strength. In cases where the back stress is sufficiently high, the dislocation source may halt dislocation emission, creating significant stress concentration between soft and hard domains, consequently causing local stress and strain and ultimately leading to crack formation. The comprehension of these mechanisms provides a valuable reference for developing FeNiAl alloys with exceptional mechanical properties. [ABSTRACT FROM AUTHOR]

In recent times, newly unveiled 2D materials exhibiting exceptional characteristics, such as MBenes and MXenes, have gained widespread application across diverse domains, encompassing electronic devices, catalysis, energy storage, sensors, and various others. Nonetheless, numerous technical bottlenecks persist in the development of high‐performance, structurally flexible, and adjustable electronic device materials. Research investigations have demonstrated that 2D van der Waals superlattices (vdW SLs) structures comprising materials exhibit exceptional electrical, mechanical, and optical properties. In this work, the advantages of both materials are combined and compose the vdW SLs structure of MBenes and MXenes, thus obtaining materials with excellent electronic properties. Furthermore, it integrates machine learning (ML) with first‐principles methods to forecast the electrical properties of MBene/MXene superlattice materials. Initially, various configurations of MBene/MXene superlattice materials are explored, revealing that distinct stacking methods exert significant influence on the electronic structure of MBene/MXene materials. Specifically, the BABA‐type stacking of CrB (layer A) and Co2CO2 MXene (layer B) is most stable configureation. Subsequently, multiple descriptors of the structure are constructed to predict the density of states of vdW SLs through the employment of ML techniques. The best model achieves a mean absolute error (MAE) as low as 0.147 eV. [ABSTRACT FROM AUTHOR]

The addition of oxygen atoms in solid solution to α‐Ti alloy can increase not only its hardness but also its brittleness. Herein, the edge dislocation mobility of Ti–O single crystals at oxygen concentrations of 0–2 at% and temperatures of 100–900 K is investigated by molecular dynamics simulations. The results show that the interstitial oxygen atoms have a strong hindering effect on the a/3 [112¯0] edge dislocations on the {1¯100} prismatic planes, which is attributed to the pinning effect of the vacancy clusters on the dislocation movement due to the interstitial oxygen atoms, thus leading to pronounced dislocation strengthening and hardening. The critical resolved shear stress (CRSS) for dislocation movement increases with increasing oxygen content and decreases with increasing temperature. Moreover, the effect of oxygen concentration on dislocation mobility also diminishes with increasing temperature. [ABSTRACT FROM AUTHOR]

Layered metal composites have been widely used in various industries fields because of their excellent properties and are responsible for mechanical behavior of materials. This paper focuses on analyzing the deformation mechanism of the (110) interface under different loading states by MD. The results show that there are two yield points in the stress–strain curve under both Z- and Y-axis loading states. The first yield is the nucleation of dislocations at the interface, meantime the slip of dislocations and the extension of stacking faults begin at the Al layer. The second one, the dislocation passes through the interface, nucleates and emits toward the Cu layer at the interface, leading to a stress mutation. It is worth noting that during the stable rheological stage, the deformation mechanisms vary under different loading directions. Under Y-axis tensile loading, the phase transformation of FCC–HCP is present due to the interaction of dislocation movement and stacking fault. On the contrary, there are two twin paths A and B, improving the strength, during Z-axis compression loading. For other loading modes, there are three zones, namely the elastic stage, the release of energy, and strain hardening and dynamic softening. The interface plays the role of nucleation, annihilation and penetration of dislocations, and this interface-dislocation mechanism is reflected in the whole stage of plastic deformation. The results have an insight into the design and control in heterointerface. [ABSTRACT FROM AUTHOR]

The mechanism of plastic deformation under tensile and compressive loading of hexagonal close-packed (HCP)/face-centered cubic (FCC) biphasic titanium (Ti) nanopillars at different temperatures (70 K, 150 K, 300 K and 400 K) and different FCC phase sizes (2 nm, 4 nm, 6 nm and 8 nm) was investigated by molecular dynamics (MD). The plastic deformation is mainly concentrated in the FCC phase during compression loading. The HCP/FCC interface is the main source of 1 6 〈 1 ̄ 2 ̄ 1 〉 Shockley partial dislocations. As the temperature increases, the dislocation nucleation rate increases and the surface dislocation source is activated. During tensile loading, it is more likely that the Shockley partial dislocations react with each other in the FCC phase to form Lomer–Cottrell sessile dislocations and stacking fault (SF) nets. When the temperature is reduced to 70 K, tensile twins are formed at the phase interface. The plastic deformation is dominated by twins and 〈 c + a 〉 dislocation slip occurs in the HCP phase. The effect of the FCC phase size on the plastic deformation mechanism of the nanopillar is strong. The FCC phase is transformed into the HCP phase when the FCC phase size in the nanopillar is reduced to 4 nm under compressive loading. However, twin deformation occurs at the HCP/FCC interface when the FCC phase size is reduced to 2 nm under tensile loading. [ABSTRACT FROM AUTHOR]

In this paper, molecular dynamics method was used to design the grain boundary (GB) segregation structure of solute atom Mo in nanocrystalline nickel, and the effect of the segregation structure on the migration and deformation mechanism of nanocrystalline Ni–Mo alloy boundaries was studied. The results indicate that the addition of solute atom Mo can cause segregation at GBs, and the yield strength and tensile strength of nanocrystalline Ni are significantly increased through solid solution strengthening. Mo atoms segregation result in an increase of the GB thickness and stability of the GB. In addition, by labeling GB atoms and tracking their diffusion trajectories, it was found that after adding Mo atoms, the probability of atomic diffusion at GBs decreased. This indicates that Mo atoms reduce GB energy and improve GB stability. Meanwhile, as the Mo content increases, the degree of atomic disorder increases, and the probability of GB migration decreases. This leads to the inability of grains to merge and inhibit their growth, effectively improving the mechanical properties of the material. As the strain increases, the number and length of dislocations increase, and a large amount of entanglement occurs at GBs. With the increase of Mo content, the number of dislocations decreases sharply, with Shockley dislocations having the highest number. Shockley dislocations interact with other dislocations and hinder their generation and movement, forming a more stable dislocation system structure and increasing the strength of the alloy. Our work focuses on observing the influence of GB segregation structure on the mechanical properties and deformation mechanism of nanocrystalline polycrystalline Ni–Mo alloys, establishing the mechanism of the influence of segregation structure on the stability and coarsening of nanocrystalline metal GBs, examining the influence of segregation structure on dislocation motion and GB migration process during deformation, and proposing positive research and development ideas and theoretical basis for designing nanocrystalline metal materials with excellent performance. [ABSTRACT FROM AUTHOR]

This study investigates the impact of initial temperature on the microstructure and mechanical properties of welded components, using molecular dynamics (MD). The stress–strain curves of the welded components, following various initial temperature treatments, revealed a double yielding phenomenon. Notably, there was a significant strain difference of 19.7% between the two yields. When the strain was loaded to the point of doubling yielding, stacking faults and twins covered the aluminum component part, while no such observations were made in the nickel component part. Additionally, tensile cracking occurred in the aluminum component part. The results indicate that treatment at varying initial temperatures alters the internal structure of the welded components. After the material yielded the first time, a significant number of disordered atoms and Shockley partial dislocations emerge, resulting in a substantial buildup of dislocation tangles and reduced dislocation migration rates. Consequently, the material exhibits a phenomenon of double yielding, with dislocation slip and deformation serving as the primary mechanisms. The optimal mechanical properties of the welded components achieved an initial temperature of 200 K. Additionally, the effect of tensile temperature on the mechanical properties of the welded components were analyzed, and similar observations of double yielding were made. The significant number of dislocation tangles served as a barrier to dislocation slip, effectively enhancing the material's mechanical properties. The simulation results provide theoretical support for the development of aluminum–nickel multilayer film self-propagation welding process. [ABSTRACT FROM AUTHOR]

Gradient nanostructured metals have become one of the research hotspots in the field of materials science due to their excellent mechanical properties and unique deformation behavior. In our contributions, the nanotwin gradient was introduced into the nanocrystalline Ni–Co alloy, and the influence of the gradient structure on the shear properties and microscopic deformation behavior was studied in order to reveal the strengthening mechanism. The gradient nanotwin Ni–Co alloy has elastic deformation and work hardening at the initial shear stage. The stress decreases after reaching the stress limit, and the uniform plastic deformation is maintained at the later stage. The excellent stability of fine twin layer and its effective hindrance to dislocation nucleation and movement can improve the strength of the material. In addition, the yield and work hardening of nanotwin gradient Ni–Co alloy are easy to occur at low temperature, and the stress–strain curve fluctuates obviously. At high temperature, the alloy is prone to plastic deformation, and the strength is reduced macroscopically. The higher the temperature is, the more difficult it is to yield. The results provide a solid theoretical basis for the design of Ni‐based alloys. [ABSTRACT FROM AUTHOR]

Gradient nanograined Ti (GNG Ti) samples were produced by a surface rolling treatment. The mechanical properties were evaluated by microhardness and tensile tests. The results indicated that GNG Ti achieved an optimized combination of strength and ductility relative to the free-standing nano/ultrafine-grained Ti. The deformation and fracture mechanisms were studied using transmission electron microscope (TEM) and scanning electron microscope (SEM). As the grain size reduced from the coarse-grained (CG) matrix to the nano/ultrafine-grained (NG/UFG) layer, the transition from conventional plastic deformation mechanisms, such as dislocation activity and twinning deformation, to grain boundary-mediated deformation mechanisms, such as stress-inducing grain growth, was identified. At the early stage of tensile deformation, the microcracks were first initiated in the CG and deformed grain (DG) regions rather than in the NG/UFG region and the CG/DG interface had a deflection effect on crack propagation. After tensile failure, the fracture morphology showed a mixture of ductile dimples and shear band-like regions. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations are performed to investigate the nanoscale tribology behavior of Ti-based FeCoNiTi High-entropy alloy (HEA) coating through nanoscratching. Three coating interface models, (001) HEA ||(0001) Ti , (001) HEA ||(11 2 ‾ 0) Ti , and (001) HEA ||(1 1 ‾ 00) Ti , are selected to explore the effects cutting depth (D) and cutting velocity (V) of abrasive particles during the nanoscratching process. The results show that the Ti-based HEA coating with the interface (001) HEA ||(0001) Ti has the smallest coefficient of friction (COF) making it most suitable as the coating interface. The increase in V resulted in the increase of the frictional force influenced by the Other structure composed of disordered atoms. Due to the existence of multiple phase structures in the limited area of the coating, dislocation nucleation is difficult and disordered atoms are formed. This is different from the strengthening caused by dislocation accumulation in the scratching region. The HEA coating plays an effective role in protecting the pure Ti substrate. With the protection of HEA coating, dislocation slip and deformation twinning were not observed in the pure Ti substrate. However, dislocation slip are the main plastic deformation mechanisms of uncoated pure Ti. These findings provide a theoretical reference for upgrading the wear resistance of pure Ti with HEA coating and expands the area of application of pure Ti. [Display omitted] • Cutting of depth and velocity affect the friction behavior of Ti-based HEA coating. • Other structure composed of disordered atoms strongly affects the frictional force. • With the protection of HEA coating, the Ti substrate has no plastic deformation. [ABSTRACT FROM AUTHOR]

Using first principles calculations, we have confirmed the electronic and optical properties of 2D kagomes graphene doped with IVA elements (Si, Ge, Sn, Pb). The results show that Si-doped system has higher structural stability. The doping system increases the band gap of single-layer kagomes graphene, with Sn doping system being the most pronounced, and therefore can be considered as an attractive material for optoelectronic devices. The difference charge density and bonding population verify that the covalence of doping atoms and C atoms decreases, and that the degree of covalence diminution increases with increasing atomic number. The undoped kagomes graphene exhibits a strong light absorption capacity in the ultraviolet region, and the absorption peaks value decreases after doping, indicating that the element doping has a great weakening effect on the light absorption capacity, which has a certain potential significance for this material to be used as the antireflection film and wave permeable material of solar cells. In addition, the Pb and Sn-doped models possess the highest and lowest static dielectric constants, respectively. The peak value of electron energy loss is lower in the range of ultraviolet and visible wavelengths. These characteristics demonstrate that kagomes graphene offers substantial potential in the areas of optoelectronic and microelectronic devices. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were performed with a Finnis-Sinclair many-body potential to investigate the mechanical properties and deformation mechanisms under applied uniaxial tensile and compressive loads in α-titanium (Ti) single-crystal nanopillars oriented along the 〈 1 1  2 ¯  0 〉 direction. The results indicate that the mechanical properties and plastic deformation mechanism display tension–compression asymmetry. The non-linear elastic behavior is attributed to the difference in friction between the neighboring atomic planes at the elastic deformation stage under push and pull loading conditions. Increasing the friction leads to hardening with compression. Decreasing the friction leads to softening with tension. Increasing the friction may also lead to higher yield stress with compression compared with tension. Perfect nanopillars are yielded via the nucleation and propagation of { 1 ¯  0 1 0} 〈1  2 ¯  1 0 〉 dislocations on the surface and corners of the nanopillars. Prismatic slip is the dominant mode of plastic deformation in the Ti nanopillars under compressive loading. However, {1 0  1 ¯  1} 〈1 0  1 ¯ 2 ¯ 〉 twinning is the dominant plastic deformation mechanism together with prismatic slip under tensile loading. Two typical intrinsic stacking faults (SFs) with different propensities exist in the nanopillars. The microstructural evolution of the SFs was also simulated. [ABSTRACT FROM AUTHOR]

In concentration gradient (CG) nano-polycrystalline Ni-Co alloy, the deformation mechanism of each region is different with the increase of Co content. It is found that in the Co-free region, grain boundary diffusion and dislocation slip mechanisms are dominant, while in other regions, there is a synergistic effect of solid solution strengthening. Moreover, the formation of new small grains by the migration of GB atoms will assist in the deformation of large grains, and the alloy exhibits gentle and stable stress–strain curve pattern. Meantime, although the dislocation density of each region is different, the dislocation density still changes stably before and after shearing. Compared with the uniform structure, the flow stress fluctuation is small when the CG structure is plastically deformed, which proves that this kind of structure is more stable. Moreover, it is found that at different temperatures, the CG alloy also shows stable dislocation density and coordination of various mechanisms, which ensures the strength stability. It is revealed that the CG structure has important properties that make the material strength more stable. This work demonstrates the excellent properties of CG alloy and has positive guiding significance for the development of low-cost, high-performance materials in terms of theoretical and practical applications. [ABSTRACT FROM AUTHOR]

The tensile deformation behavior is studied in pure titanium (Ti) nanopillars subjected to loading along the [0 0 0 1] orientation based on molecular dynamics (MD) simulations. The double yielding phenomenon is displayed in stress-strain curves when the deformation temperature is less than 380 K. One new type of deformation-induced phase transformation from the hexagonal close-packed (hcp) to face-centered cubic (fcc) phase has been predicted. The effects of temperature and strain rate on this type of phase transformation are systematically investigated. It is revealed that { 1 0 1 ¯ 2 } 〈 1 0 1 ¯ 1 〉 twinning plays an essential role in inducing the phase transformation, which is produced through dislocation glide of multiple Shockley partial dislocations inside the { 1 0 1 ¯ 2 } 〈 1 0 1 ¯ 1 〉 twin. A group of high-density stacking faults is accumulated though the continuous glide of multiple Shockley partial dislocations inside the twinning region, eventually leading to the allotropic phase transformation from the hcp to fcc phase. After twinning, two thermally activated dislocation slip processes compete with one another: Shockley partial dislocations and full dislocation slip. The deformation mechanism changes from phase transformation to dislocation slip when the temperature is higher than 380 K or the strain rate is lower than 10 8 s −1 . The dislocation slip on the { 1 0 1 ¯ 1 } pyramidal plane is clearly observed under tensile loading at higher temperatures. Furthermore, our simulations indicate that the nucleation rate has a strong effect on the deformation mechanism on the nanoscale. [ABSTRACT FROM AUTHOR]

The Charpy impact toughness of Ti–2.5Al–2Zr–1Fe alloy plate with a bimodal and normal grain size distribution was comparatively studied. The sample with the bimodal grain size structure exhibits the larger impact absorbed energy and lower anisotropy than that with the normal grain size structure, which is mainly attributed to the coordination of prismatic slips in the fine α grains and { 10 1 ‾ 2 } 10 1 ‾ 1 deformation twins in the coarse α grains. The current work provides a promising approach for improving impact toughness and reducing anisotropy through microstructure optimization in near-alpha Ti alloys. • An improved impact absorbed energy and decreased anisotropy were obtained in Ti–2.5Al–2Zr–1Fe alloy with bimodal grain size. • The improved impact absorbed energy was attributed to the prismatic slip associated with the twining inducing plasticity. • Microstructural optimization can improve the impact toughness and reduce anisotropy of near-alpha titanium alloys. [ABSTRACT FROM AUTHOR]

• Native and nonnative English students used a similar number of p-frames in essays. • Native English students used more p-frames with high predictability and fixedness. • Native English students overused more participant-oriented p-frames. • Nonnative English students overused more text-oriented p-frames. A phrase frame (i.e., p-frame) is a type of recurrent discontinuous multiword sequence. So far, many studies have investigated the p-frames used in written texts in various genres, disciplines, and registers. However, few previous p-frame studies have attempted a comparative analysis of the p-frames used by native and nonnative English students. This scarcity prevents us from obtaining a full understanding of phraseological competence development in nonnative English learners. Using a corpus-driven approach, the current study identified and compared the 5-word p-frames used by native and nonnative English students in their college essays. The results showed no statistically significant difference between these two groups with respect to the types and tokens of p-frames used in their essays. However, significant intergroup differences could be observed when the predictability, variability, structural characteristics, and discourse functions of the identified p-frames were considered. These findings on the use of p-frames by native and nonnative English students could complement the comparative studies of recurrent continuous multiword sequences and thus advance our understanding of phraseological competence development in nonnative English learners. [ABSTRACT FROM AUTHOR]

Different size effects and deformation mechanisms are revealed in α-titanium (Ti) single crystal nanopillars orientated for [112̄0] and [0001] based on molecular dynamics simulations. The strength–size relationship changes from “smaller is stronger” to “smaller is much weaker” when the width of nanopillars reduces from 19 nm to 3 nm. The “smaller is much weaker” is attributed to that the surface effect caused by a thermal vibration of surface atoms leads to the initiation and growth of surface dislocations. [ABSTRACT FROM AUTHOR]

An inverse “smaller is stronger” trend is predicted on the basis of molecular dynamics simulations of α-titanium (Ti) single-crystal nanopillars orientated for double prismatic slips when the nanopillars are less than 7 nm wide. This trend is attributed to a significant increase in the surface energy due to the nucleation and propagation of edge dislocations on the surface of the pillars. [ABSTRACT FROM AUTHOR]

The Charpy impact absorbed energy of a hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy plate with different sampling and notching directions was investigated. Strong anisotropic variations occurred in impact absorption energies due to difference of the α phase crystal orientation and microstructural characteristics along different directions. The higher crack propagation energy of the sampling-notching direction sample (RD-ND) resulted in an impact absorption energy of approximately 2.5 times larger than that of the TD-ND, TD-RD and RD-TD samples. Based on the analysis of the α crystal orientation and the TEM microstructure after impact deformation, it was found that the higher absorption energy of the RD-ND sample was attributed to the activities of a large number of { 10 1 ‾ 0 } ⟨ 1 2 ‾ 10 ⟩ prismatic slips and the resistance created by grain boundaries against crack propagation, which also resulted in the delamination of the impact fracture surface. Finally, the coupling effect of crystallographic texture and microstructural characteristics on the impact deformation mechanisms of the hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy was described. • A strong anisotropy of the impact energy in A hot-rolled Ti6321 alloy plate is observed due to the coupling effect of the microstructural characteristics and the crystal orientation of the α grains. • The RD-ND orientation sample exhibits the highest impact absorbed energy due to the activity of a large number of { 10 1 ‾ 0 } 1 2 ‾ 10 prismatic slips and the barrier effect of grain boundary on crack propagation during impact loading. • The coupling effect of crystallographic texture and microstructural characteristics on the impact deformation mechanisms were established. [ABSTRACT FROM AUTHOR]

In this contribution, molecular dynamics method is used to accurately add quantitative Co atoms in the grain boundary (GB) region of nano-polycrystalline Ni to study the effect of solute atoms on the GB and the deformation mechanism of the material. It was found that adding an appropriate amount of Co atoms at the GBs can improve the tensile strength of the material to a certain extent through solid solution strengthening. However, excessive introduction of solute atom will increase the activity of GB atoms, destroy the stability of GBs, and accelerate the appearance of material yielding. At the same time, the Co atoms at the GB gradually detached from the GB region and diffused into the grains. In addition, the dislocations are distributed in a grid at the GBs, and with the increase in strain, the number and length of dislocations gradually increase, forming a large number of entanglements. Moreover, the Shockley dislocation interacts with other dislocations to form a more stable dislocation structure by hindering the generation and movement of other dislocations, which greatly enhances the strength of the system. [ABSTRACT FROM AUTHOR]

In practice, most components often receive impact loads during service. In order to ensure the service safety of components, impact toughness evaluation is essential. To the best of our knowledge, the previous studies were mainly focused on the quasi-static tensile deformation, and the impact toughness of bimodal grain structured metals have rarely been reported. Three different grain size characteristics TA3 alloy, i.e., fine grained sample (FG Ti), the mixture of coarse and fine grained sample (MG Ti), and coarse grained (CG Ti), were produced, and their tensile and Charpy impact properties were comparatively investigated. Owing to the strengthening of retained β phase and the twining inducing plasticity effect, MG Ti display the highest tensile strength and impact absorbed energy, together with an intermediate tensile elongation. The impact deformed microstructures revealed that the primary deformation modes of FG Ti, MG Ti and CG Ti sample are: dislocation slips, a combination of dislocation slip in fine grained region and { 10 1 ¯ 2 } deformation twins in coarse grained region, and { 11 2 ¯ 1 } deformation twins in sequence. [ABSTRACT FROM AUTHOR]

The fatigue crack growth (FCG) behaviors of a twin inducing plasticity (TWIP) Ti-5Al-1 V-Sn-1Zr-0.8Mo (Ti5111) alloy with three typical microstructures were investigated. Compared with the equiaxed and bimodal structures, the lamellar structure exhibited a higher resistance to the FCG rate, but it displayed a lower strength and elongation to failure. Many 10 1 ¯ 2 10 1 ¯ 1 deformation twins (DTs) spanning multiple α/β layers were observed in the lamellar structure near the FCG path. The same type of DT was also observed in the equiaxed structure, although its density was significantly lower than that of the lamellar structure, and no DTs were found in the bimodal structure. The higher resistance to FCG of the lamellar structure results from its large effective microstructural unit size (α colony), which is most favorable to deflecting cracks and increasing crack path tortuosity, and is associated with the blocking effect of deformation twin boundaries on crack propagation. • Compared with equiaxed and bimodal structure, the lamellar structure exhibits the highest resistance to FCG rate. • The high resistance to FCG of lamellar structure is due to the coupling effect of crack deflection and twin boundary barrier. • Deformation twins spanning multiple α/β layers were observed in lamellar structure near the fatigue crack propagation path. [ABSTRACT FROM AUTHOR]

The effects of gradient grain size and temperature on the mechanical properties of nanocrystalline nickel were studied by the molecular dynamics method, and the microstructure change process of size gradient nanocrystalline nickel under tensile load was characterized by Common Neighbor Analysis (CNA). The research results show that dislocations tend to generate stress concentration in small-sized grains during stretching, so the plastic deformation of the material always occurs in small-sized grains first. At the same time, through Dislocation Analysis (DXA), it was found that Shockley dislocation is the main factor affecting its mechanical properties, and the interaction between dislocations provides a certain contribution to the strength of the metal. In addition, yield strength, maximum tensile stress, and Young's modulus all decrease with increasing temperature, and the grain boundary atomic content and the degree of disorder are greatly increased. During the stretching process, the number of dislocations is greatly reduced, which leads to a reduction of their interactions, which is the reason for the reduction of the mechanical properties of the material. The above research results have positive meaning for the design of gradient nanocrystalline materials, and provide reference and help for the improvement of nanomaterial properties. [ABSTRACT FROM AUTHOR]

Mechanical behavior and plastic deformation mechanism of a new type of Co30Fe16.67Ni36.67Ti16.67 high entropy alloys (HEAs) have been calculated by the molecular dynamics method. The results show that the polycrystalline Co30Fe16.67Ni36.67Ti16.67 HEA has remarkable tensile plasticity and anisotropy. When the crystallographic orientation of the grain is <001>, the plastic deformation mechanism is face‐centered cubic (FCC)→body‐centered cubic (BCC) transformation and deformation twins. Grain boundary and vacancy reduce the nucleation energy of FCC→BCC phase transition, making BCC phase nucleation easy and growing in a shear manner, eventually forming deformation twins in the BCC phase. When the crystallographic orientation of grain is <110> and <111>, the plastic deformation mechanism is stacking faults, FCC→hexagonal‐close‐packed (HCP) phase transformation, and deformation twins. The motion of Shockley dislocation leads to the stacking fault, intrinsic stacking fault leads to the FCC→HCP phase transition, extrinsic stratification fault leads to the twin deformation, and the grain refining occurs during the tension process. Temperature and strain rate also have strong effects on tensile strength and elastic modulus. These results will provide a theoretical basis for the development of the HEAs and expand their application. [ABSTRACT FROM AUTHOR]

Potassium (K) metal anodes are the most competitive candidates for low‐cost and high‐energy density rechargeable batteries. However, uncontrolled K dendrite growth strictly impedes the practical application of K metal anodes. Herein, a potassiophilic and conductive dual‐gradient free‐standing host (named TS‐PKS) composed of the bottom layer with Ti3CN and F doped SnO2 (F‐SnO2) and the top layer with perfluorinated sulfonic acid K (PFSA‐K) and ordered mesoporous silica (SBA15) is constructed to achieve dendrite‐free K deposition. The potassiophilicity and conductivity of the TS‐PKS host increase along with the depth direction to generate a bottom‐up dual‐gradient of K+ affinity and electroconductivity. Such bottom‐up dual‐gradient of K+ affinity and electroconductivity can synergistically manipulate uniform K metal deposition following the bottom‐up manner, preventing the notorious K dendrite growth. As a result, the TS‐PKS@K symmetric cell can stably cycle over 2800 h at 0.5 mA cm−2/0.5 mAh cm−2. Meanwhile, the TS‐PKS@K//PTCDA full battery also exhibits an initial specific capacity of 118.3 mAh g−1 at a high current density of 500 mA g−1 and maintains up to 81.1 mAh g−1 after 1000 cycles. This novel dual‐gradient strategy design offers a straightforward approach to effectively manipulate K metal deposition manner for achieving dendrite‐free K metal anodes. [ABSTRACT FROM AUTHOR]

Lexical bundles perform discourse functions and present differing levels of variability, with some slots replaceable by optional words. Incorporating both function and formulaicity perspectives is a promising approach to uncover certain features of these recurrent language patterns. Based on the variability measurement and functional taxonomy proposed by Biber (2009) and Biber et al. (2004), this study compared the extent to which the lexical bundles from research articles of applied linguistics and pharmaceutical sciences are fixed. Thereafter, the lexical bundles were examined across the discourse functions to explore the possible interaction between function and variability. The results indicate that variability shows disciplinary variation, with bundles from applied linguistics articles as a whole being relatively less fixed. In addition, discourse functions are found to be closely associated with variability. These findings shed light on the question of whether lexical bundles are prefabricated patterns and may facilitate the teaching of academic writing at the graduate level. [ABSTRACT FROM AUTHOR]

The influence of microstructure (bimodal and lamellar structure) on the fatigue crack growth (FCG) rate of Ti–6Al–3Nb–2Zr–1Mo alloy was investigated using compact-tension (CT) specimens. The da/dN curves showed that the FCG rate of lamellar structure was slower than that of bimodal structure, especially in the early stage of crack growth. The FCG paths in the early stage were observed by optical microscopy and scan electric microscopy. The results revealed that the FCG paths of lamellar structure were more tortuous than that of bimodal structure. The frequency of crack deflection and bifurcation of the lamellar structure is significantly higher than that of bimodal structure. The dominant mode of crack propagation for bimodal structure is crossing βtrans and αp, and for lamellar structure is crossing α colonies. Fatigue crack growth mechanisms at the early stage have been studied by observation of crystalline orientation near the crack propagation path at the crack tip, in combination with the slip trace analyzing. The results show that the fatigue crack growth directions in αp or βtrans for bimodal structure and α colony for lamellar structure are mostly consistent with that of prismatic or basal plane trace. This indicated that the cracks propagation modes of crossing αp or βtrans in bimodal structure and crossing α colonies in lamellar structure are resulting from the slip band cracking of the microstructure at crack tip, as the evidence of { 10 1 ‾ 0 } 11 2 ‾ 0 prismatic dislocation lines were observed in αp or βtrans for bimodal structure and α colony for lamellar structure by transmission electron microscope (TEM) near the fracture surface. • The da/dN curves showed that the FCG rate of lamellar structure was slower than that of bimodal structure, especially in the early stage of crack growth. • Cracks propagation modes were evaluated by EBSD-assisted slip trace analysis. [ABSTRACT FROM AUTHOR]

Herein, the effects of different Co content and temperature factors on the shear mechanical properties of nano‐polycrystalline nickel–cobalt alloy are analyzed by molecular dynamics (MD) simulations. It is found in the work that the highest shear modulus of 63.03 GPa is obtained when the Co content is 10%, attributed to the lattice distortion caused by the difference in the lattice parameters between two elements. During the shearing process, the multilevel twins are present with intensification of the deformation process, resulting in excellent dynamic shear performance. Shockley dislocations will drive the stacking faults and other partial dislocations to constitute a tetrahedral edge, and finally forms a tetrahedral structure. In addition, as the temperature of the shear environment increases, the highest strain and stress decrease. The grain boundary atoms increase significantly, and the atoms inside the grains decrease accordingly. As the degree of atomic disorder increases, the grain boundaries will melt gradually. The decrease of partial dislocation density can weaken the entanglement effect caused by dislocations. The previous conclusions promote the product development and application of nano‐polycrystalline alloys in the future, and provide important guidance significant for the engineering application of nickel–cobalt alloys. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were utilized to investigate the mechanical properties of the Al–Co–Cr–Fe–Ni high-entropy alloy and observe atomic microstructure and internal dislocation line changes under different parameter conditions. The findings demonstrate that the mechanical properties of the AlCoCrFeNi3 high-entropy alloy are significantly superior to those of conventional alloys in ambient temperature. During the tensile process, the face-centered structure undergoes interconversion with other structure types, while the internal dislocation lines gradually increase. The presence of grain boundaries impedes dislocation movement, resulting in lower deformation capacity and tensile strength in polycrystals compared to single crystals. Enhancing Ni content, increasing strain rate, and decreasing temperature during tensile process contributes to the enhancement of the mechanical properties of material. Among these factors, the Ni content exerts the most significant influence on the mechanical properties of the material. [ABSTRACT FROM AUTHOR]

As a novel two-dimensional nanomaterial, MXene is one of the most promising alternative electrode materials due to its large specific surface area, good electrical conductivity, excellent mechanical properties and tunable structure. This paper investigates the electrochemical performance of the MXene materials Zr 2 N and Zr 2 NS 2 as anode materials for lithium and sodium ion batteries. The results showed that on the Zr 2 N monolayer, lithium and sodium ions tended to adsorb at the C site, while on the Zr 2 NS 2 monolayer, lithium and sodium ions tended to adsorb at the B and A sites, respectively. The results of the Charge difference density diagram and Mulliken population analysis show that there is a significant electron transfer between the adsorbed metal ions and the material surface. This indicates that lithium and sodium ions form chemisorption on the Zr 2 N and Zr 2 NS 2 surfaces. The high theoretical specific capacity and low migration barrier suggest that Zr 2 N and Zr 2 NS 2 are promising anode materials for lithium and sodium ion batteries. • The electrochemical properties of Zr 2 N and Zr 2 NS 2 as anode materials for lithium and sodium ion batteries are analyzed and discussed. • The high theoretical specific capacity and low migration barrier suggest that Zr 2 N and Zr 2 NS 2 are promising anode materials for lithium and sodium ion batteries. • It provides positive theoretical guidance for the experiment. [ABSTRACT FROM AUTHOR]

Nanotwinned exist in crystals as coherent interfaces with low interfacial energy, which can not only improve the strength of metal materials, but also increase the ductility. In this manuscript, we have performed molecular dynamics simulations of the mechanical properties of a nano-columnar crystalline Cu-Ni alloy with different twin boundary spacing. It is found that the model without twin has a stacking fault tetrahedron composed of stair-rod dislocations, which results in a small change in dislocation density at the later stage of deformation, and the average stress after yielding is lower than that of the model with twin. During the deformation process, with the increase of Other atoms, the dislocation slip barrier is enhanced, the tensile strength is increased, and the yield phenomenon is delayed, which is more obvious with the decrease of twin boundary spacing. The dislocation density decreases with the decrease of the spacing of the twin boundary, and the dislocation segments become shorter. When the twin boundary spacing is 0.625 nm, the tensile strength is increased by about 71% compared with the model without twin structure. [ABSTRACT FROM AUTHOR]

Grain boundary engineering is an effective and feasible metal strengthening strategy to enhance the properties of nanopolycrystalline alloys by changing the number, configuration, and connectivity of different types of grain boundaries, especially for the twin boundaries. In the present contribution, the effect of twin spacing and loading mode on the deformation behavior and mechanism of NiCoAl columnar polycrystalline alloy is investigated. The results show that the nanotwins can not only increase the bearing capacity of dislocations but also emit many dislocations, resulting in the coupling effect of dislocation strengthening and twin strengthening. When the twin spacing is large, intrinsic stacking faults occur and gradually transform into deformation twins. In this stage, Shockley partial dislocation controls plastic deformation. When the twin spacing is small, the high‐density twin layers and stacking faults are more likely to interweave, showing a combination action of Shockley partial dislocation and stair‐rod dislocation. With the loading changing to Z axis, the yield strength decreases due to reduced resistance to the dislocation and a weakened number of Shockley partial dislocations of the emission, leading to less strengthening of the twins. The insights provide a solid theoretical foundation for the further application of NiCoAl in industrial production. [ABSTRACT FROM AUTHOR]

Ni–Co alloy has high temperature resistance, corrosion resistance, excellent magnetic and catalytic capabilities, and is widely used in energy development, chemical industry, electronics, aviation and aerospace, such as combustion chamber hot end parts, aircraft engine working blades and hydrogen evolution catalysts. It is well known that the properties of materials depend on the structure and morphology, which depend on the preparation method. At present, the main methods for preparing nano-Ni–Co alloy are electrodeposition, sol–gel method and solution reduction method. The parameters in these preparation methods affect the morphology and properties of nano-Ni–Co alloy, so it is particularly important to study the influence of various parameters on the properties of Ni–Co alloy. In this work, the preparation methods and research progress of nano-Ni–Co alloy in recent decades are summarized, hoping to provide valuable information for the development of Ni–Co alloy. [ABSTRACT FROM AUTHOR]

In this paper, the effects of rare earth elements on the bonding strength and stability of TiC/fcc-Fe interface are explored by using the first-principles method based on density functional theory. The results show that the Ti terminal is more stable than the C terminal in the process of forming the interface. The alloying elements tend to segregate at position 2 on the side of fcc-Fe. The segregation of Mo, Nb, Cr and Ce alloying elements increases the interatomic electron cloud enrichment and consumption between the interfaces and enhances the Fe–Ti interactions. The d orbitals of Mo, Nb, Cr and Ce and f orbitals of Ce have strong hybridization with Fe-d orbitals and Ti-d orbitals electrons near the Fermi energy level, indicating an increase in bonding strength and stability of the interfaces. When Fe atoms are replaced by W, Ni and Al atoms, the covalent bond strength between interfacial atoms is reduced, thus weakening the interfacial bonding strength. This provides solid theoretical foundation with regard to further application in austenitic heat-resistant steel fields. [ABSTRACT FROM AUTHOR]

We use first-principles calculations in this contribution to study electronic structures and optical properties, especially absorption and reflectivity spectra, dielectric constant and loss function of Li, Na, K, Be, Mg, Ca and Al adsorption behaviors on (2 0 0) surface of hexagonal silicon nitride (β-Si 3 N 4 ). The lower adsorption energy of −3.931 eV for Ca-adsorbed surface indicates that it has more excellent structural stability. The seven kinds of adsorptions are all featured by chemisorption with commonly negative value of adsorption energy, implying relatively abated capacity of defending the chemical corrosion formed by metals mentioned above. Band gaps of surfaces with different adsorptions are 0.113 eV, 0.099 eV, 0.113 eV, 0.147 eV, 0.154 eV, 0.151 eV and 0.111 eV for Li-, Na-, K-, Be-, Mg-, Ca- and Al-adsorbed surface structure, respectively, along with 0.143 eV for clean surface of β-Si 3 N 4 , which leads more efficient measures of potential for obtaining outstanding semiconductor properties for materials. Moreover, absorption spectra curve of surface drops to a lower peak value of 5.46 × 10 4  cm −1 , 4.94 × 10 4  cm −1 and 3.53 × 10 4  cm −1 for Na-, Mg- and Ca-adsorption, decreasing by 10.0%, 18.6% and 41.8% in contrast to clean surface, 6.07 × 10 4  cm −1 , respectively, in which the surface carries decreased reflectivity spectra and dielectric loss that are greatly valued and expected in solar cell industry, indicating its broader application potential in photoelectric and microelectronics devices fields. [ABSTRACT FROM AUTHOR]

Electronic structures and optical properties of zinc-blende aluminum nitride doped with transition metals are investigated. Lu-doped system possesses the most considerate stability with the lowest formation energy of −9.033 eV compared to others. Band structures of systems are introduced to investigate a more excellent semiconductor capacity for Re-doped system with a band gap (EG) of 0.689 eV, with others having band gaps of 2.120, 2.159, 1.806, 1.837 and 0.879 eV, respectively, much smaller than that of pristine one, 3.113 eV. Moreover, absorption spectra curve reaches the lowest peak of 2.558×105cm−1 for Os-doped system; simultaneously, the system exhibits a relatively negative reflectivity spectra and dielectric loss of 5.620 eV that are extensively expected in solar cell industry, predicting its broad scope of application prospects in photoelectric and microelectronic devices. [ABSTRACT FROM AUTHOR]

Bandgap tailoring of β-Si3N4 is performed by single and co-doping by using density functional theory (DFT) of PBE functional and plane-wave pseudopotential method. The results reveal that a direct bandgap transfers into an indirect one when single-doped with As element. Also, a considerate decrease of bandgap to 0.221 eV and 0.315 eV is present for Al–P and As–P co-doped systems, respectively, exhibiting a representative semiconductor property that is characteristic for a narrower bandgap. Compared with other doped systems, Al-doped system with formation energy of 2.67 eV is present for a more stable structure. From charge density difference (CDD) maps, it is found that the blue area between co-doped atoms increases, illustrating an enhancement of covalent property for Al–P and Al–As bonds. Moreover, a slightly obvious “Blue shift” phenomenon can be obtained in Al, Al–P and Al–As doped systems, indicating an enhanced capacity of responses to light, which contributes to the insight for broader applications with regard to photoelectric devices. [ABSTRACT FROM AUTHOR]

Based on first-principles simulations with the generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) functional, we studied the electronic structures and optical properties of hexagonal silicon nitride (β-Si3N4) doped with IV A elements, C, Ge, Sn and Pb. It was found that the Ge-doped system is characterized by a more stable structure with a lower formation energy of 2.584 eV compared with those of the C-, Sn- and Pb-doped systems of 3.877 eV, 5.249 eV and 7.672 eV, respectively. The band gap (EG) of the Pb-doped system was the lowest at 1.6 eV, displaying semiconducting characteristics. Additionally, there was a transition from a direct band gap to an indirect band gap in the C-doped system. Charge difference density analysis showed that the covalent property of the C-N bonds was enhanced by expansion of the electron-free region and the larger Mulliken population values of 0.71 and 0.86. Furthermore, lower absorption and reflectivity peaks at 11.30 eV were observed for the C-doped system, demonstrating its broader potential for application in photoelectric and microelectronic devices. [ABSTRACT FROM AUTHOR]

Molecular dynamics was used to study the uniaxial tensile process of Ni–Co alloy with gradient nanotwin structure, and the microstructure and deformation mechanism of mechanical properties of gradient nanotwin Ni–Co alloy were studied from the micro perspectives of dislocation, twin layer and grain boundary movement. The results show that when the twin structure Ni–Co alloy is uniaxial stretched along the gradient direction and perpendicular to the gradient direction, the twin layer has different strengthening effects on the structure and strengthening mechanism, the stretching in different directions has greater influence on the dislocation movement and stacking fault nucleation of the nanogradient twin structure. The yield strength of Ni–Co alloy is 11.3 Gpa and 5.5 Gpa, respectively, after stretching along gradient and vertical gradient directions, Young's modulus reaches 221.16 Gpa and 127.90 Gpa. It is found that the gradient twin structure stretched along gradient direction has greater strength and the twin layer breaks into fragments and distributes in the system during the process of strain increase. At different temperatures, it was found that the strength and plasticity of the material decreased sharply with the increase of temperature, the dislocation density in the system also decreased with the increase of temperature, resulting in poor performance of the material. [ABSTRACT FROM AUTHOR]

The Nb 2 NT 2 /MoTe 2 heterojunction shows n -type Ohmic contacts in O terminal system, while p -type and n -type Schottky contacts are formed in F and OH terminal systems, respectively, which makes the system suitable for electron device in terms of bandgap engineering controlling. [Display omitted] • The Nb 2 NT 2 /MoTe 2 heterostructure is dominated by vdW interaction. • The equilibrium interlayer spacing is within the range of 3.061 Å to 3.328 Å. • 0.12 e per cell spontaneously transfer from MoTe 2 to Nb 2 NO 2 layer. • n -type Ohmic contacts are formed in O terminal system. • Schottky contacts are formed in F and OH terminal systems. In the current effort, a novel attempt to construct heterojunctions using Nb 2 N two-dimensional MXene materials with fascinating property and MoTe 2 transition metal disulfide compounds is proposed. The effect of vertical strain on the electronic structure and interfacial contact properties of the heterojunction is investigated by first principles calculations. The O, F, and OH functional groups prefer to be adsorbed on top of the N atoms of the Nb 2 N MXene material. The configuration III of heterojunction has the lowest energy and stable model, and the equilibrium layer spacing is within the range of 3.061 Å to 3.328 Å, indicating that they belong to typical vdW heterojunctions. The large work function difference between the two components induces the transfer and rearrangement of charge. 0.12 e per cell spontaneously transfer from MoTe 2 to Nb 2 NO 2 layer. In contrast, the Nb 2 NF 2 and Nb 2 N(OH) 2 layers transfer 0.01 e and 0.21 e to the MoTe 2 layer, respectively. n -type Ohmic contacts are formed in O terminal system, while p-type and n -type Schottky contacts are formed in F and OH terminal systems, respectively. Additionally, for vertical strain, with the decrease of the layer spacing, the p-type Schottky barrier height (SBH) decreases from 0.270 eV to 0.095 eV in former system, meanwhile the n -type Schottky barrier height in the latter system also decreases from 0.260 eV to 0.156 eV. These regulations of interest lays a theoretical foundation for bandgap engineering and Schottky junction preparation and opens a window into MXene-based heterojunction electron device. [ABSTRACT FROM AUTHOR]

The electronic structure and photocatalytic properties of two-dimensional GaSe/MoS 2 heterostructure are systematically studied by first-principles calculation. It is found that it could be used as a potential visible light catalyst to decompose water into H 2 and O 2. The lattice mismatch rate is 3.55%, and the binding energy was −0.446 eV, indicating that it has a stable configuration. An indirect band gap of 2.255 eV with hybrid HSE06 functional is observed, which falls into a wide range of visible light absorption. It exhibits II-type band alignment and this can promote the spatial separation of photogenerated carriers. In addition, the band edge spans the redox potential of water, indicating that heterostructure can produce hydrogen by photocatalytic decomposition H 2 O. The electrons transfer from GaSe to MoS 2 layer, while the holes do the opposite, thus improving the photocatalytic efficiency. Therefore, GaSe/MoS 2 heterostructure has broad application prospects in photocatalysis. • The GaSe/MoS 2 heterostructure is a very promising photocatalyst. • Work function of a material plays a momentous role in the band alignments. • The density of state can show the mechanism behind the orbital reconfiguration. • Semiconductor photocatalysis is considered as an ideal way to convert solar energy into chemical energy. [ABSTRACT FROM AUTHOR]

In this paper, the adsorption behavior of Na atom on T-carbon (111) surface is investigated in detail by first principles calculations. The adsorption of Na atom on the T-carbon (111) surface is a chemical adsorption with excellent stability. The minor opening of the bandgap is present. The charges transfer from Na atom to C atom, which leads to a transition of the bonding properties from covalence to ionicity. For the H-site adsorption system, the adsorption energy is the lowest, indicating that the system is the most stable. At the same time, C-Na has the lowest bond population, indicating its strong ionic property. Additionally, the dielectric loss of the adsorbed system reduces, especially for the H-site adsorption, which is conducive to the improvement of the service life in electron material devices. In absorption spectrum, the peak values decrease and shift to the lower energy direction, resulting in the appearance of redshift phenomenon. The reflection peak and energy loss values are greatly reduced, in which the trend is most obvious for the H-site adsorption. The above analysis results provide a theoretical basis for the application of photosensitive devices and open a window on the design and control the micro-nano devices. [ABSTRACT FROM AUTHOR]

• Low-cycle multiaxial fatigue experiments of Q355D notched specimens under different loadings were carried out. • The important factors affecting fatigue life of notched specimens were analyzed by three correlation analysis methods. • A modified MGM (1, N) model was established by fine-tuning the time series of the GM (1, N) model. • A new fatigue life prediction method for notched specimens was proposed. The paper aims to analyze the stress–strain response of building steel under low-cycle multiaxial fatigue and to accurately evaluate the fatigue life of specimens by selecting the more important relevant factors that affect fatigue behavior. Based on this, low-cycle multiaxial fatigue experiments of Q355D notched specimens under different multiaxial loading are carried out. Firstly, the fatigue behavior of notched specimens under different loadings and the relationship between the biaxial strain amplitude ratio and fatigue life are analyzed. Secondly, Grey correlation analysis, Pearson correlation analysis, and Random Forest importance analysis are used to screen out the important factors affecting fatigue life. Finally, the grey MGM (1, N) model is used to predict the fatigue life of notched specimens, and the results show that the predicted life based on Random Forest importance analysis is in good agreement with the experimental life. In this paper, the multiaxial fatigue problem is decoupled into two sub-problems, i.e. screening out related factors and life prediction based on the related factors, which can be used as a reference for life prediction in structural design. [ABSTRACT FROM AUTHOR]

Exploring the next generation of invincible energy materials with fascinating properties is vital in the challenge of energy crisis. In this paper, we extract T-carbon as a potential candidate and have an insight into the electronic and optical properties by means of first principles. It is found that S1 position doping system is relatively more stable with the formation energy of 0.323 eV, and has the smallest bandgap value of 1.228 eV. Charge density difference maps show that the electron loss is obvious near the S atom and the covalent bond is weakened. The population analysis shows that the S atom will obtain electrons through competition, while the Se atom will lose electrons. Additionally, the peak values of 2 in the doped systems decrease significantly, especially for S2 doping system, indicating that S2 doping can effectively improve the service life in related devices. Compared with the instinct system, the absorption coefficient is lower in the UV region and greater in the visible region. The peak of energy loss spectrum reduces after doping, especially for Se1 doping. The results provide a theoretical basis for the industrial application of T-carbon in the energy microdevice fields. [ABSTRACT FROM AUTHOR]

Interfacial segregation engineering is widely used as a means of regulating the strength and toughness of materials. In this paper, the effect of alloying elements on the interfacial segregation and interfacial bonding properties of fcc-Fe/NbC is investigated with the precipitated phase NbC in austenitic heat-resistant steel. The results show that there are eighteen interfacial configurations between the fcc-Fe and NbC phase, and the stability of the interface with Nb terminal is better than that of C terminal according to the calculation results of separation work and interface energy. Al atom is easy to segregate on the surface of austenite, while the alloy elements Mo, Nb, Cr, Ti, Mn, Y and Zr tend to segregate in the austenite matrix. The segregation of alloy elements Mo, Nb, Cr and Ti can enhance the hybridization between the d orbits of Fe and Nb atoms at the interface, thus promoting the bonding strength of the interface, while the segregation of Mn, Al, Y and Zr reduces the covalent interaction of the interface atoms, which weakens the bond strength at the interface. The above results have important practical significance for improving and regulating the composition and interfacial properties of heat-resistant steels. • Six fcc-Fe(111)/NbC(111) interfaces with different interface terminations are studied by first-principles. • The work of separation of the Nb-terminated interface is greater than that of the C-terminated interface. • The interface of the C-terminal is unstable. • Alloying elements affect the bonding strength of interfacial atoms. [ABSTRACT FROM AUTHOR]

In this effort, the influence of alloying element doping on fcc-Fe (111)/NbN (111) interface property is investigated by means of first principles. The interface structure combined with 5-layer fcc-Fe and 7-layer NbN is selected for investigation, because they exhibit characteristic consistent with the bulk counterpart. By calculating the interface energy, separation work and phonon spectra, the results show that interface 6 is stable. The alloying elements are more easily segregated at position 2 in the interface and it is chosen as the object of study. After Co and V doping, the separation work of the interface increases and the interfacial energy decreases. The degree of charge density consumption around them is greater than that of the intrinsic interface, indicating that the covalent bonds between atoms have been enhanced. This indicates that doping with Co and V atoms can improve the stability of the interface, which is consistent with the results towards population analysis and density of states. On the contrary, after doping with Zr, Sc, Y, and Ti atoms, the interatomic covalence weakens and the interface stability decreases. Especially for Y doping, the lowest electron consumption and the smallest electron cloud enrichment in the middle layer can be observed, demonstrating the worst interface stability. This insight has important guiding significance for the interface segregation behavior of alloying elements, and provides a theoretical basis for the development of next generation austenitic stainless steel. • Studied the effect of segregation of alloying elements Ti, Co, Zr, Y, V, Sc on fcc-Fe (111)/NbN (111). • After doping with Co and V atoms, the covalence between atoms is enhanced. • After doping with Co and V atoms, the interface stability can be improved. [ABSTRACT FROM AUTHOR]

Probabilistic fatigue evaluation is the key to ensure the service integrity of large-sized mechanical equipment, but in practical engineering, the probabilistic fatigue models coupled with multiaxial stress conditions and small sample information characteristics are still insufficient. Accordingly, the virtual subsample augmentation method is effectively coupled with the improved Bootstrap method to propose a general probabilistic fatigue evaluation process. Specifically, the random sample regeneration method is first used to expand the small sample fatigue data, and then life distribution information under different stress levels is fused based on the backwards statistical inference method, the P-S-N curve is fitted with the integrated life dispersion information. Secondly, a new fatigue damage parameter based on the inhibition function is proposed to modify the P-S-N curve and predict fatigue life. Meantime, the multiaxial fatigue test of Q355(D) alloy steel with different notch sizes is carried out, and the model is verified in conjunction with existing fatigue test data of TC4-DT alloy and TC4 alloy. The results show that the proposed model has a certain universality for notched specimens, the modified stress field intensity method can accurately characterize the impact of notch and size effects on fatigue damage of specimens. [ABSTRACT FROM AUTHOR]

This article addresses a problem of spacecraft orbit estimation with measurement transmission restrictions through an event-triggered state estimation approach. Specifically, we consider the scenario that the ground station communicates with the spacecraft through multiple channels and each channel decides whether or not to transmit the measurements to the spacecraft based on separate deterministic event-triggering conditions. Considering $J_2$ perturbations, an event-triggered unscented Kalman filter-based state estimation algorithm is designed on the basis of a model of orbit dynamics and a measurement model of the ground station. The performance of the estimator is evaluated based on real-time two-line element data. The obtained results indicate that the proposed algorithm can achieve satisfactory estimation performance at reduced measurement transmission rates. [ABSTRACT FROM AUTHOR]

The stabilization of grain boundaries (GBs) is beneficial for improving the stability and mechanical properties of nanocrystalline (NC) metals. Molecular dynamics (MD) calculations were performed to investigate the shear response of Ni Σ 17 [110](223) symmetrical tilt GB. It was found that under the action of shear, the nucleation and evolution of the GB source Shockley partial dislocations ultimately result in the low-energy-state transformation of the GB structure units (SUs). However, the Ag atom contained in the GB increases the shear stress and strain required for the GB relaxation, and the strain range for the GB relaxation is expanded, indicating the inhibitory effect of the Ag atom on the structural relaxation of Ni Σ 17 [110](223) GB. As the temperature increases from 10 K to 250 K, the structural relaxation of Ni Σ 17 [110](223) GB becomes easier to proceed. In addition to segregation-induced GB stabilization, strain-induced GB relaxation and the roles of foreign atom and temperature clarified in this work could provide several new entry points for stabilizing high-energy GBs. [ABSTRACT FROM AUTHOR]

How to improve the diffusion coefficient of Lithium ions in active materials is very necessary, which is responsible for the electrochemical performance. In this present contribution, LiFe 10/12 Co 1/12 Mn 1/12 P 11/12 S 1/12 O 4 (LF(CM)P(S)O) are designed and the stability, lithium ion diffusion rate, lithium intercalation potential, discharge curve, and electronic performances are systematically explored. The LF(CM)P(S)O shows the better stability with the formation energy of 2.01 eV. The lithium ion diffusion barrier of the system is reduced from 1.02 to 0.57 eV after doping, predicting that the lithium ion diffusion rate in LF(CM)P(S)O is 10 orders of magnitude faster than that of intrinsic system. The characteristic transition from p-type to n-type semiconductor is present due to the doping of S, and the doping of Mn and Co leads to the generation of impurity bands and the reduction of band gap from 3.78 to 0.737 eV. The effective mass of electrons in the doped system is 1.59m 0 , much greater than 1m 0 , which is conducive to the improvement of its conductivity. The charge density difference and electron localization function (ELF) demonstrates that the disappearance of electron enrichment and the decrease of the localization are responsible for the rapid migration of the lithium ion. The high operating voltage, charge-discharge platform of 4.7 V and the voltage difference contribute to the promotion of electrochemical performance, which open a window for the commercialization application of Li-ion battery. [ABSTRACT FROM AUTHOR]