Influences of symmetric tilt grain boundary on the stretching deformation behaviors of Cu bicrystals

The microstructure of grain boundary (GB) becomes an important factor affecting the strength of nanomaterials during plastic deformation. In this work, Cu bicrystals with different coincidence site lattice (CSL) interfaces are constructed, and the influences of the symmetric tilt interface on the mechanical properties and plastic deformation behaviors during uniaxial tension are studied by molecular dynamics simulation. The results indicate that the peak stress of tensile stress-strain curves for most bicrystals is lower than its monocrystalline samples, except CSL3, CSL11 and CSL57 bicrystals with a continuous and single structural unit. The CSL3 bicrystal has the highest strength, while CSL33 bicrystal has the lowest strength among all the tested samples. The CSL11 and CSL57 bicrystals with a lower GB energy have a higher stability of interface, which delays the yielding. Moreover, the generation of twin and stair-rod dislocation at the interfaces strengthens the CSL11 and CSL57 bicrystals. The CSL3 almost has the same parameters as its monocrystalline sample S3, massive research has confirmed that the sample with a higher density twin (CSL3 interface) exhibits higher combined properties of strength and plasticity. This work may provide a guideline for GB engineering to improve material properties by controlling the GB structure.