In the present paper, the dislocation-precipitate interaction in the Inconel 718 superalloy is studied by means of molecular dynamics simulation. The atomistic model composed of the ellipsoidal $N{i}_{3}Nb$ precipitate (γ″ phase) and the $Ni$ matrix is constructed, and tensile tests on the composite $N{i}_{3}Nb@Ni$ system along different loading directions are simulated. The dislocation propagation behaviors in the precipitate interior and at the surface of the precipitate are characterized. The results indicate that the dislocation shearing and bypassing simultaneously occur during plastic deformation. The contact position of the dislocation on the surface of the precipitate could affect the penetration depth of the dislocation. The maximum obstacle size, allowing for the dislocation shearing on the slip planes, is found to be close to 20 nm. The investigation of anisotropic plastic deformation behavior shows that the composite system under the loading direction along the major axis of the precipitate experiences stronger shear strain localizations than that with the loading direction along the minor axis of the precipitate. The precipitate size effect is quantified, indicating that the larger the precipitate, the lower the elastic limit of the flow stress of the composite system. The dislocation accumulations in the precipitate are also examined with the dislocation densities given on specific slip systems. These findings provide atomistic insights into the mechanical behavior of nickel-based superalloys with nano-precipitates.

Due to their compositional complexity and flexibility, multi-principal element alloys (MPEAs) have a wide range of design and application prospects. Many researchers focus on tuning chemical inhomogeneity to improve the overall performance of MPEAs. In this paper, we systematically review the chemical inhomogeneity at different length scales in MPEAs and their impact on the mechanical properties of the alloys, aiming to provide a comprehensive understanding of this topic. Specifically, we summarize chemical short-range order, elemental segregation and some larger-scale chemical inhomogeneity in MPEAs, and briefly discuss their effects on deformation mechanisms. In addition, the chemical inhomogeneity in some other materials is also discussed, providing some new ideas for the design and preparation of high-performance MPEAs. A comprehensive understanding of the effect of chemical inhomogeneity on the mechanical properties and deformation mechanisms of MPEAs should be beneficial for the development of novel alloys with desired macroscopic mechanical properties through rationally tailoring chemical inhomogeneity from atomic to macroscale in MPEAs.

The effects of dynamic strain aging (DSA) on residual stresses generated in Ni-base superalloys during heat treatments are not well understood. In this study, the residual stress field induced by water quenching an IN718 disc while undergoing DSA is studied using coupled thermo-mechanical finite element (FE) analyses in conjunction with neutron diffraction (ND) measurements. A visco-plastic constitutive model that incorporates the effect of DSA is proposed to describe the experimentally observed negative strain rate sensitivity and abnormal temperature dependence phenomena in the stress–strain response of solid solution treated IN718. The predicted quenching residual stresses in the disc agree well with the ND measurements. Due to the DSA, a propagating high plastic strain rate region can be identified in the disc during the early stages of the quenching process. Due to the negative strain rate sensitivity and abnormal temperature dependence effects caused by DSA, the predicted residual stresses are approximately 10% greater than when those two effects are not accounted for. The effects of different convection heat transfer conditions in the FE model are examined and discussed. It is found that the convection heat transfer coefficients have a great influence both on the disc residual stresses and DSA-related plastic strain rate field predictions.

A physically-based elasto-viscoplastic constitutive model is proposed to examine the size effects of the precipitate and blocks on the creep for martensitic heat-resistant steels with both the dislocation creep and diffusional creep mechanisms considered. The model relies upon the initial dislocation density and the sizes of M₂₃C₆ carbide and MX carbonitride, through the use of internal variable based governing equations to address the dislocation density evolution and precipitate coarsening processes. Most parameters of the model can be obtained from existing literature, while a small subset requires calibration. Based on the least-squares fitting method, the calibration is successfully done by comparing the modeling and experimental results of the steady state creep rate at 600° C across a wide range of applied stresses. The model predictions of the creep responses at various stresses and temperatures, the carbide coarsening and the dislocation density evolution are consistent with the experimental data in literature. The modeling results indicate that considerable effect of the sizes of precipitates occurs only during the creep at relatively high stress levels where dislocation creep dominates, while the martensite block size effect happens during creep at relatively low stress levels where diffusion creep dominates. The size effect of M₂₃C₆ carbide on the steady creep rate is more significant than that of MX precipitate. The present study also reveals that the two creep mechanisms compete such that at a given temperature the contribution of the diffusion creep mechanism decreases with increasing stress, while the contribution of the dislocation creep mechanism increases.

This work proposes a crystal plasticity-based micromechanical finite element model to account for the inelastic crystallographic slip in an aluminium alloy and its effect on the development of micro-voids. Three-dimensional unit cell with periodic boundary conditions is used to represent the porous single crystal, which is subject to multiaxial external loads with constant stress triaxiality. The effects of stress triaxiality and crystallographic orientation on the ductile failure response for the porous single crystal are then quantified. Through the Taylor–Reuss mean field homogenisation, the stress–strain responses for porous polycrystal under multiaxial stress states are also investigated and compared with the conventional modelling results. The present work indicates that void coalescence strain at single crystal level strongly depends on the crystallographic orientation, particularly when stress triaxiality is low, and the overall stress–strain response of porous polycrystal can be affected by the crystallographic slip-based micro-void growth and polycrystallinity of the material.

Ti-6Al-4V (TC4) alloy is widely used in aerospace and biomedical applications due to its excellent strength-to-weight ratio and corrosion resistance. Its plastic deformation behavior is strongly influenced by its microstructural characteristics, particularly grain size. In this study, a crystal plasticity model incorporating a Hall–Petch relationship was developed to simulate the plastic deformation of TC4, with explicit consideration of the effect of grain size on slip resistance. The model employs a thermally activated flow rule to describe the kinetics of slip systems, enabling accurate prediction of flow stress and strain hardening across different microstructural conditions. The model is calibrated and validated using experimental stress–strain data from uniaxial tensile tests on specimens with varying grain sizes. Simulation results demonstrate that the model successfully captures the grain-size-strengthening effect and predicts the corresponding evolution of local strain heterogeneity. Furthermore, a critical local equivalent plastic strain criterion was established, which effectively predicts the dependence of macroscopic failure strain on grain size. This work provides a physically based computational tool for optimizing TC4 processing parameters and predicting deformation under service conditions.