Influence of Segregation Structures on the Mechanical Behavior of Nanocrystalline NiAl Alloys

This study establishes a grain boundary segregation structure model and investigates the influence of boron (B) segregation at grain boundaries with varying concentrations on the simulated tensile behavior of the alloy through molecular dynamics simulations. The results indicate that the introduction of segregated atoms at grain boundaries effectively enhances both yield strength and plastic deformation capability. By comparing the mechanical properties of models with different segregation concentrations, it is found that without segregated atoms, grain boundary stability is poor, while excessive segregation concentration leads to increased disordered structures and reduced strength. The optimal performance is achieved when the segregation atom concentration is near its solubility limit (1.5%). The introduction of segregated atoms effectively lowers the average potential energy of grain boundary atoms, increases the relaxed grain boundary region, and forms a skeleton‐like structure that firmly anchors the grain boundaries, thereby enhancing their stress‐bearing capacity and making them less prone to fracture and deformation. In the later stages of plastic deformation, as dislocation activation intensifies, the well‐preserved grain boundary structure significantly pins dislocation motion, further improving the alloy's strength.