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Grain boundaries are important microstructures in metallic materials, and dislocation nucleation on grain boundaries plays a crucial role in material deformation. Studies on P segregation on grain boundaries typically focus on segregation behavior at substitution or interstitial positions. Less attention is given to the interaction of a certain amount of P with dislocation nucleation and grain boundary structural units during deformation. Previous deformation mechanism studies often qualitatively determine mechanisms, struggling to quantitatively explain their roles. This paper offers an atomic mechanism for grain boundary dislocation nucleation, aiding in understanding of the effect of P segregation in BCC Fe on mechanical properties. In this paper, a large-scale atomic/molecular massively parallel simulation (LAMMPS) program was employed. It investigated the effect of P segregation in BCC Fe grain boundary on the tensile deformation behavior. Binary Fe-P embedded atom potential was used for the calculation of stress-strain curves and dislocation activation energy densities. The analysis of P segregation behavior on different grain boundary structures and the effect of temperature was conducted using visual analysis software (OVITO.3.10). To illustrate the elastic-plastic component of the strain during loading, a set of kinematic parameters based on continuum medium mechanics was employed. The atomic deformation tensor of the deformation gradient was calculated using the nearest-neighbor table approximation of the continuum medium field around each atom. Additionally, the mechanisms of dislocation nucleation and twinning were discussed for the symmetrically inclined grain boundaries in BCC Fe. For the (111) grain boundary system, dislocation nucleation extends and dominates the deformation behavior. For the (112) twin grain boundary system, tensile deformation is mainly controlled by twin grain boundary, resulting in BCC-FCC phase transitions. Tensile loads were applied to different grain boundaries at temperatures of 300 K and 600 K. The results indicate that, in the Fe-P system with P concentrations ranging from 0.05at.% to 0.2at.%, compared to enhancing the strength of (111) grain boundary systems, P segregation leads to a decrease in strength for (112) systems, but the effect is minor. The P segregation hinders dislocation nucleation on the (111) and (113) grain boundaries, while it promotes dislocation nucleation at (112) grain boundaries, and P segregation has no significant effect on dislocation nucleation at (114) grain boundaries. The degree of deformation of the E structural unit at the P segregated site on the (111) grain boundary is small, and the dislocations are more inclined to nucleate in the unsubstituted structural unit near the P atom.

Core structural materials such as cladding in advanced nuclear reactors face harsh service environments such as high-temperature, and their comprehensive performance is one of the bottlenecks restricting the development of advanced reactors. Mo and its alloys are key candidate, but pure Mo suffers from a lack of high-temperature strength. Mo-based alloys are superior to pure Mo in terms of mechanical properties. Research found that the addition of a certain amount of Re, W, Ti, Zr, C and other elements will enhance the high-temperature strength of Mo-based alloys. The effects produced by the ingredients are very complex and cannot be found in great detail by testing. Now materials genetic engineering, based on the prediction of data-driven material properties and optimization, shortening the cycle of materials research and development, and thus speed up the process of the entire field. Thus a CNN regression model based on Bayesian optimization was constructed based on the data obtained from literature research and preliminary experiment. The collected Mo-based alloy dataset contained 220 samples and 38 compositions as well as test temperature characteristics of tensile with the target variable being tensile strength. Found that the Re, C, O, N, Ti, Zr, Nb, La, W, Hf, Ta, Si, and Ni have a higher weight on the target value, and C, Ti, and Zr positively affect the tensile strength. Re, O, N, La, W, Hf, Ta, Si, and N have a negative tendency to correlate the characteristics with the tensile strength. Using the R2 value as an evaluation metric, the model is able to achieve 0.832 6. Combined with correlation analysis and modeling prediction analysis, it is concluded that Ti, Zr, Re and La2O3 are beneficial to the enhancement of high-temperature tensile strength of Mo-based alloy. N and Si are not conducive to the enhancement of tensile strength of Mo-based alloy at high-temperature. According to the correlation analysis conclusion, the effect of the coupling of these compositions C-Zr, Nb-Hf-Ta, Ni-Si, N-O and Zr-Ti on the tensile properties of the materials at high-temperatures will be considered subsequently, along with the simultaneous enhancement of toughness. Subsequently, by analyzing the influence of the combination of two elements or three elements on the change of tensile strength, it can get the composition design scheme that the tensile strength of Mo-based alloy reaches a certain range under specific temperature conditions.

The elemental segregation behaviors and interactions between point defects and symmetrical tilt grain boundaries (GBs) in TiVTa concentrated solid–solution alloys (CSAs) have been studied through hybrid Monte Carlo/molecular dynamics (MC/MD) simulations. A pure V model, a random TiVTa CSA with randomly distributed elements, and an equilibrated TiVTa CSA with Ti segregation were constructed to investigate the influence of chemical disorder and local elemental segregation on defect–GB interactions. For defect–GB interactions, GBs interact more strongly with interstitials than with vacancies. Compared with the pure V, the vacancy absorption length scale of GBs is greater, whereas the interstitial absorption length scale of GBs is shorter in TiVTa CSAs due to the chemical fluctuation and local lattice distortion. This means a higher recombination efficiency of point defects in TiVTa CSAs. The elemental (Ti) segregation in TiVTa CSAs can further enhance the sink strength of GBs towards interstitials, while simultaneously reducing their sink strength towards vacancies. Consequently, the preference effects of GBs towards interstitials and vacancies are amplified in the equilibrated CSA due to local ordering, thereby reducing efficient defect annihilation around GBs. These results provide fundamental insights into the irradiation defect dynamics of CSAs with body-centered cubic (bcc) structure. [ABSTRACT FROM AUTHOR]