Grain boundary segregation of Al alters alloy deformation behavior

Grain boundary segregation engineering can tailor the mechanical and physical properties of nanocrystals by segregating solute or impurity atoms at grain boundaries. In this study, the segregation behavior of solute element Al at grain boundaries in nanocrystalline NiCoAl alloy was designed, and the effect of Al segregation with different contents on the deformation mechanism of nanocrystalline alloys was investigated from an atomic perspective. The results show that Al segregation at grain boundaries significantly enhances grain boundary stability, and as Al content increases, grain boundary energy becomes lower and more stable, with grains being less prone to growth and coarsening. In addition, increasing Al content inhibits the occurrence of phase transformations and stacking fault networks, thereby making the formation of the BCC phase difficult, as this phase is characterized by higher strength and lower plasticity. Grain boundaries’ dislocation-blocking capacity is reduced, and this reduction ultimately results in alloy softening and improved plasticity. Furthermore, Shockley partial dislocations dominate the plastic deformation of nanocrystalline alloys, and the number of perfect dislocations and Shockley partial dislocations decreases as Al content increases. Our work provides valuable insights into the microscopic deformation mechanisms associated with solute element segregation.