Mechanical properties and crack extension of nanocolumnar polycrystalline copper with grain boundary segregation

Abstract

A nanocolumnar polycrystalline copper (NCPC) model containing prefabricated cracks with random grain orientation is constructed and modified with a high-entropy grain boundary. The effects of crack length, location, and grain boundary modification on the tensile mechanical properties and crack extension behavior of NCPC are investigated by uniaxial tensile simulation by LAMMPS. Once the crack length exceeds 1 nm (limiting threshold), the peak stress in NCPC decreases significantly with increasing prefabricated crack length. Peak stress and yield limit of NCPC are dramatically enhanced after high-entropy grain boundary modification. High initial dislocation density and strong dislocation pinning due to the high-entropy grain boundaries significantly enhance the tensile mechanical properties of NCPC. The crack extension rate of high-entropy grain boundary-modified polycrystalline copper is faster than that of NCPC, and there is a more obvious difference in the crack growth evolution. The crack extension of high-entropy grain boundary-modified polycrystalline copper is mainly driven by grain boundary slip, which leads to the extension along the direction of an “X-type” shear band, while the crack extension of NCPC consists of a combination of grain dislocations and grain boundary slip.