Effect of high angle grain boundary on plastic deformation and fracture of micro-bicrystal copper: An in-situ SEM experimental and multiscale simulation study

SJ Wan and TH Yu and T Su and TC Yu and YB Yan and FZ Xuan, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 942, 148699 (2025).

DOI: 10.1016/j.msea.2025.148699

The effect of the high angle grain boundary (HAGB) on the plastic deformation of microscale copper (Cu) was studied using micro-tensile specimens of Cu bicrystal with 7 2 7 and 1 1 11 orientations, respectively. In situ SEM observation revealed that deformation primarily concentrated in the 1 1 11 oriented grain, indicating that the presence of HAGBs restricted the transmission of dislocations between grains due to the mismatch in grain boundary slip. Crystal plasticity finite element simulations and extended finite element simulations revealed that the first activated slip system was (- 111)0-11, rather than the system that was typically expected to dominate deformation due to its higher Schmid factor. This transition was attributed to the influence of HAGB geometry, which played a key role in determining the activation sequence of slip systems and led to crack initiation at the HAGB. To directly observe the nucleation and motion of dislocations, molecular dynamics simulations further confirmed that the HAGB acted as a favorable site for dislocation nucleation and effectively impeded dislocation transmission across the boundary. This work revealed the significant role of HAGBs in governing dislocation dynamics and crack initiation in microscale copper, providing valuable insights for improving the mechanical properties of bicrystalline materials.

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