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Establishing the correlation between grain boundary (GB) structure and energy is crucial for advancing the fundamental understanding of polycrystalline materials, yet this correlation remains elusive. In this study, systematic atomic simulations are performed to comprehensively explore numerous GBs in different FCC metals and alloys. The findings unveil a universal linear relationship between the GB energy and GB structural orderliness parameter (GB excess centrosymmetry or excess bond orientational order parameters). Remarkably, the identified linear relationship proves universally applicable across different metal systems, GB types, and length scales, rooted in the linear correlation between atomic potential energy and atomic structural orderliness. Furthermore, the ratio between GB energy and orderliness parameter emerges as a potent indicator for gauging the extent of GB relaxation, thereby providing valuable insights to inform the design of nanocrystalline materials with enhanced GB stability. The universal linear relationship between grain boundary energy and structural orderliness parameters, revealed by high-throughput atomic simulations. [Display omitted] [ABSTRACT FROM AUTHOR]

• A general micromechanics-based model for effect of inhomogeneous lattice distortion on precipitate strengthening and fracture toughening is developed. • Effects of lattice distortion on grain boundary migration and crack growth in Fecocrnimn HEA are quantified. • The synergistic strengthening effect of lattice distortion and precipitate is investigated. • The lattice distortion strain field counteracts some of applied stress and raises the critical stress for crack extension. High-entropy alloys (HEAs) usually exhibit exceptional mechanical properties attributed to one of important core effects for serious lattice strain to impede dislocation motion compared to the traditional alloys. However, their roles on the quantitative measurement for precipitate strengthening and fracture toughness are lack using the existing physical model. Here, we propose a mechanistic modelling to study effect of heterogeneous strain caused by lattice distortion on the precipitate strengthening and fracture toughness in the HEAs, and then verify this role using atomic simulation. The results indicate that the lattice distortion and precipitate synergistically impede the grain boundary migration, increasing the strength. In the dilute alloy with a low lattice distortion, the grain boundary migration process is less sensitive to the precipitate size. The stress field generated by the lattice distortion relieves the stress concentration at the crack tip under external force. This in turn alleviates the accumulation of dislocations and reduces the probability of crack extension. Furthermore, the heterogeneous strain caused by lattice distortion counteracts some of the applied stress and raises the critical stress for crack extension, which enhances the plasticity and the critical stress intensity factor. The developed unified model would be applicable to high entropy ceramics in similar scenario. [ABSTRACT FROM AUTHOR]

• GB improves irradiation resistance via absorbing irradiation defects. • Universally exponent function between GB absorption rate and energetic state is captured. • GB resistance is strongly improved attributed to disorder-induced entropy change. • Ni segregation is particularly enhanced, contributing to high GB absorption rate. Multi-principal element alloys (MPEAs) demonstrate significant promise as structural materials for nuclear energy equipment owing to their exceptional mechanical properties and radiation-resistant performances. In these alloys, the grain boundary (GB) serves as a crucial microstructure that typically mitigates irradiation damage by absorbing the irradiation-induced defect. However, the micromechanisms governing the anti-irradiation performance of GBs in MPEAs remain unclear. In this study, we investigate the irradiation defect production during collision cascade in the model NiCoCr bicrystal system through atomic simulations, aiming to unveil the atomic-scale origin of GB to resist irradiation damage in MPEAs. The results reveal that GBs effectively serve as sinks for irradiation defects in NiCoCr. The sink efficiency depends on the GB energetic state, including GB excess energy and defect segregation energy, as well as the energetic difference between interstitial and vacancy segregation. Statistical analysis identifies a universally exponent function between the defect absorption rate at GB and GB energetic state. In NiCoCr, the GB-disorder-induced-entropy increase leads to a biased reduction in interstitial segregation energy, narrowing the gap between interstitial and vacancy segregation energies by approximately 11 % compared to Ni. This improvement enhances the overall resistance of GBs to irradiation damage. Additionally, preferential segregation of Ni interstitial atoms is notably enhanced in NiCoCr, contributing to a high defect absorption rate at GBs. This study provides new insights into the resistance of GBs to irradiation defects in MPEAs and suggests GB engineering as an effective strategy for developing advanced alloys with enhanced radiation tolerance. [Display omitted] [ABSTRACT FROM AUTHOR]

Exploring the interactions between precipitates and grain boundaries (GBs) is of great important to tailor the high-temperature stability and mechanical property of precipitate hardened alloys. However, the influence of precipitate on GB stability in high entropy alloys (HEAs) is still uncovered at nanoscale. In this work, we investigate the effects of precipitate size and temperature on grain boundary migration (GBM) using molecular dynamic simulations. The results show that the GB stability is improved with the increase of the precipitate size, especially at low temperatures. Compared with the traditional dilute alloys, the strong atomic lattice distortion exits in HEAs, resulting in the localized high tensile/compressive stresses. Thus, GB bends towards the indeterminate direction due to the lattice distortion, different with the case bending towards precipitate in the dilute alloys. In addition, the lattice distortion makes dislocation nucleate at random GB region in HEA, which is different from that in dilute alloys. High temperature reduces lattice distortion and relieves the localized high stresses, thereby inhibits the nucleation rate of dislocations from GB. These results provide the fundamental messages for designing novel HEAs with excellent thermal stability. • Influence of precipitates on GB stability at nanoscale is still uncovered in high entropy alloys. • Complex atomic stress field around precipitate leads to irregularly non-localized deformation of GB. • GB roughness increases due to stress field induced by precipitate and lattice distortion. • High temperature reduces lattice distortion thus relives localized high stress, thereby inhibit dislocation nucleation. [ABSTRACT FROM AUTHOR]

In-depth understanding of grain boundaries (GBs) in multi-principal element alloys (MPEAs) is considered significant for designing MPEAs by GB engineering. This work explores the nanoscale GB structure and migration mechanism in MPEAs using atomic simulations. The GB-roughening transformation is observed as the mixing entropy increases, and the effect of entropy is confirmed by thermodynamic analysis. The entropy-induced transition of GB migration is proved: 1) the "concentrated shuffling mechanism" controls the migration of ordered GBs in low-entropy systems, leading to the obviously stepwise migration; 2) the "dispersed shuffling mechanism" dominates the migration of disordered GBs in high-entropy systems, resulting in the continuous migration manner. Image, graphical abstract [ABSTRACT FROM AUTHOR]