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In this study, molecular dynamics simulations is used study the mechanism of diamond abrasive polishing on mono-crystalline silicon containing circular inclusions. The variation in coordination number, polishing force, friction coefficient, potential energy, scratching temperature, and dislocation were analyzed and studied by changing the size of inclusions in monocrystalline silicon. The analysis of coordination number indicates that the number of silicon atoms with the coordination number of five increases with increasing inclusions, and the atoms mainly gather at the bottom of inclusions; the larger the inclusions, the deeper the subsurface damage; but after polishing, large inclusions increased the number of defective atoms recovered; the analysis of diamond structure revealed that the increase in the diameter of inclusions increases the number of damaged diamond structure atoms. The results show that the polishing force, normal force, and friction coefficient increase with increasing circular inclusion, but the effect of the size of the inclusion on the temperature is not significant; the potential energy of the system first increases obviously and then decreases slowly after reaching the peak; the number and length of dislocations decrease to 0 at first and then increase gradually.

Ni/Ni3Al heterogeneous multilayer structures are widely used in aerospace manufacturing because of their unique coherent interfaces and excellent mechanical properties. Revealing the deformation mechanisms of interfacial structures is of great significance for microstructural design and their engineering applications. Thus, this work aims to establish the connection between the evolution of an interfacial misfit dislocation (IMD) network and tensile deformation mechanisms of Ni/Ni3Al multilayer structures. It is shown that the decomposition of IMD networks dominates the deformation of Ni/Ni3Al multilayer structures, which exhibits distinct effects on crystallographic orientation and layer thickness. Specifically, the Ni/Ni3Al (100) multilayer structure achieves its maximum yield strength of 5.28 GPa at the layer thickness of 3.19 nm. As a comparison, the (110) case has a maximum yield strength of 4.35 GPa as the layer thickness is 3.01 nm. However, the yield strength of the (111) one seems irrelevant to layer thickness, which fluctuates between 10.89 and 11.81 GPa. These findings can provide new insights into a deep understanding of the evolution and deformation of the IMD network of Ni/Ni3Al multilayer structures.

Additive manufacturing of aluminum (Al) alloys has attracted significant attention in the aerospace industry. However, achieving ultrahigh-strength (>500 MPa) Al alloys remains challenging due to their intrinsic poor printability. Here, we report a novel hybrid additive manufacturing (HAM) approach to process ultrahigh-strength AlMgSc alloy, which combines laser powder bed fusion (LPBF) with interlayer ultrasonic shot peening (USP). The results show that the interlayer ultrasonic shot peening depth reached ∼700 µm, leading to almost full density and residual stress convection from tension to compression. The HAM method promotes equiaxed grain formation and refines grain due to grain recrystallizations. Interestingly, the HAM followed by aging treatment tailors the hierarchically multi-gradient structures, inhibits Mg element intragranular segregation, and promotes the multi-nanoprecipitates (e.g. Al 3 (Sc, Zr) and Al 6 Mn) precipitation. Remarkably, the HAM followed by aging treatment achieves yield strength of 609 MPa and breaks elongation of 7.5%, demonstrating ultrahigh strength and good ductility compared with other Al alloys manufactured by AM and forging as reported in the literature. The strength enhancement mechanisms in this AlMgSc alloy are discussed. The high-density Al 3 (Sc, Zr) precipitates are the main strengthening contributor, and unique hetero-deformation induced (HDI) strengthening (originates from the heterogeneous microstructures) further enhances the strength of the material. This work highlights a novel approach for processing complex-structured ultrahigh strength Al alloy components by hybrid additive manufacturing. Hybrid additive manufacturing for processing ultrahigh strength Al alloy. Hierarchically gradient microstructures involving grain and dislocation gradients. Achieved ultrahigh yield strength (>600 MPa) together with a good elongation of 7.5%. Hybrid additive manufacturing enhances strength without evidently sacrificing ductility.

Localized stress concentration and defect accumulation are prone to occurring during metal spinning because of the coupled effects of complex loading and interfacial friction. In this study, a molecular dynamics model of metal spinning was established to investigate the effects of process parameters and temperature on the mechanical response, material flow, contact loading, and dislocation evolution behavior within the contact zone. The results indicate that the optimal deformation coordination is achieved with an arc radius of 25 Å, an indentation depth of 8 Å, and a tangential velocity of 1.5 Å/ps. Analysis of the normal and tangential forces shows that the normal load is rapidly established during the indentation stage, whereas the tangential load continuously increases with material shear transport. Both loads decrease significantly with increasing temperature. Elevated temperature effectively suppresses dislocation accumulation and simplifies the dislocation structure, causing the plastic deformation behavior to gradually transition toward a dominant primary slip-system mode. This study reveals the local deformation and dislocation evolution mechanisms during spinning and provides theoretical guidance for the process optimization of thin-walled spinning components.

Context This study employs molecular dynamics (MD) simulations to investigate the mechanical properties and deformation mechanisms of titanium (Ti) nanofoam under uniaxial tensile loading. The effects of porosity (ranging from 20 to 50%), strain rate (from 5 × 10⁸ to 5 × 10⁹ s⁻ 1 ), and temperature (from 300 to 900 K) on the tensile response are systematically examined. The results reveal that increasing porosity significantly reduces the ultimate tensile strength (UTS) and elastic modulus, while intensifying localized shear strain and stress concentration. These conditions facilitate the formation of amorphous phases and grain structures, and substantially influence dislocation behavior. Furthermore, higher strain rates are found to enhance strength by increasing both UTS and elastic modulus. In contrast, elevated temperatures induce phase transformations that improve ductility but compromise strength. Overall, this work provides valuable insights into tailoring the mechanical performance of Ti nanofoams, with implications for their use in biomedical, structural, and functional applications. Methods The simulations were performed using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) package. The results were analyzed using the Open Visualization Tool (OVITO). Structural analysis was conducted using common neighbor analysis (CNA) and polyhedral template matching (PTM), while dislocation behavior was studied with dislocation analysis (DXA). Surface meshes for volume and surface computations were generated using the construct surface mesh method.

This study aims to explore the fatigue properties of polycrystalline nickel-based superalloys at the nanoscale. Molecular dynamics (MD) simulation is used to investigate the effects of strain amplitude on shear strain, dislocation patterns, atomic structure forms, and fatigue performance. The results indicate that under the same load, the accumulation of plastic damage increases with the number of cycles; at the same cycle number, there is a positive correlation between the average plastic damage degree and the strain amplitude. When the load amplitude is below 0.015, the cycle number corresponding to the maximum dislocation density shows a positive correlation with the load amplitude, while for load amplitudes above 0.0175, this relationship becomes negative. Except for a strain load amplitude of 0.015, the trend of hexagonal close-packed (HCP) atoms during the fatigue process is generally consistent, with a sudden increase around 20 cycles at a strain load amplitude of 0.015, approximately 1.8 times higher than that of other strain load amplitudes.

The formability at room temperature and low speed limits the application of aluminum alloy, while high strain rates positively improve the formability of materials. The constitutive behaviors of materials under high strain rates or impact loadings are significantly different from those under quasi-static conditions, while few constitutive models consider the effect of the mobile dislocation and forest dislocation evolution on the dynamic strain aging (DSA) over a wide strain-rate range. The 5052 aluminum alloy, of which the primary source of strain-hardening is dislocation–dislocation interaction, is widely used in manufacturing automotive covering parts and is considered one of the most promising alloys. Therefore, this study conducts uniaxial tensile tests on AA5052-O under conditions of temperatures ranging from 293 K to 473 K and strain rates ranging from 0.001 s−1 to 3000 s−1, and compares the stress–strain relationships of AA5052-O under different conditions to illustrate the constitutive relationship affected by the dislocation evolution over a wide strain-rate range. The Arrhenius model based on the thermal activation mechanism is modified and extended by considering the effects of dynamic strain aging (DSA), drag stress, and the evolution of mobile dislocation and forest dislocation. Thus, a new physics-based constitutive model for AA5052-O is proposed, which can well reflect the change in strain-rate sensitivity with the strain rate increasing. The mobile dislocation density and total dislocation density are predicted with a modified Kubin–Estrin (KE) model, and the influences of variable mobile dislocation on DSA and dislocation drag are discussed as well. In order to verify the reliability of the new constitutive model, the dislocation densities of the specimens before and after deformation are obtained with TEM and XRD, which are in good agreement with the predicted values. This study also compares the newly proposed model with classic constitutive models using multiple statistical evaluation methods, which shows that the new physics-based constitutive model has not only more clear physical meanings for its parameters but also has a higher prediction accuracy.

High-entropy alloys (HEAs) exhibit excellent machining performance due to their compositional diversity. In nanocutting, grain refinement can further enhance the material’s plastic deformation capacity and surface integrity. This study uses molecular dynamics (MD) simulations to analyze the microplastic deformation mechanisms of polycrystalline FeCoNiCrCu HEA during nanocutting, focusing on the influence of different grain sizes. By constructing polycrystalline and nanocutting models, we examine the effects of grain size on cutting forces, surface morphology, dislocation defects, and stress distribution. Results indicate that larger grains (10.47 nm) allow dislocations to propagate over longer distances, leading to a more uniform plastic deformation. In contrast, smaller grains (6.49 nm) result in stronger boundary obstruction of dislocations, leading to local accumulation, narrower shear zones, and enhanced resistance to deformation. Reducing grain size increases dislocation density and stress concentration in the cutting zone, amplifying sub-surface defect evolution. Moreover, HEAs with smaller grains demonstrate stronger resistance to deformation and reduced cutting forces during the cutting process. This research provides insights into the micro-behavior of HEAs in nanomanufacturing and guidance for precision machining processes of high-performance materials.

Intense research efforts are focused on the development of advanced high-entropy alloys intended for premium aerospace components and other applications, where high strength and good formability are crucial. The mechanical properties of these alloys are closely related to the phase transformation, dislocation evolution, and grain size, and these factors are affected by the deformation temperature. The response of the retained austenite to strain-induced martensitic transformation at various temperatures was studied in an advanced Ti68Nb7Ta3Zr4Mo18 (at.%) high-entropy alloy via molecular dynamics simulation. It was found that the Ti68Nb7Ta3Zr4Mo18 alloy changes from a single crystal to a polycrystal during the tensile process, and the transition of the Ti68Nb7Ta3Zr4Mo18 (at.%) high-entropy alloy from the BCC phase to the FCC phase occurs. At high temperatures and low strain rates, grain boundary slip is the main deformation mechanism, and at low temperatures and high strain rates, dislocation slip replaces grain boundary slip as the dominant deformation mechanism, which improves the strength of the alloy. Moreover, when the grain size is too small, the strength of the alloy decreases, which does not satisfy the fine grain strengthening theory and shows an inverse Hall–Petch relationship. This study offers a new compositional window for the additive manufactured lightweight high-strength material categories for various applications including the aerospace industry.

Grain boundary morphology and dislocation evolution during hot deformation of die steel with and without titanium as well as the size, morphology, distribution, type and the precipitation strengthening mechanism of precipitated phase were studied by means of transmission electron microscope (TEM), high-resolution transmission electron microscope (HTEM), energy dispersive spectroscopy (EDS), etc. The results show that the grain size increases and the dislocation density decreases with the increase of hot deformation temperature. There are three types of nanoscale precipitated phases of titanium-added steel as follows: the first kind is cubic shape TiC precipitated phase, the second kind is spherical VC precipitated phase, and the third kind is associated precipitated phase of Ti and V. The precipitated phase of the titanium-added steel precipitates uniformly and orderly in the interior of the grain, but the precipitated phase of the steel without titanium precipitates in agglomeration and disorderly in the interior of the grain. The size of the precipitated phase of the steel with titanium is 1.1 nm smaller than that of the steel without titanium after hot deformation at 900°C. The precipitated phase sizes of the steel with titanium under 10 nm account for 93% of the total, and the precipitation strengthening effect is significant.