On the role of Cu-Zr amorphous intergranular films on crack growth retardation in nanocrystalline Cu during monotonic and cyclic loading conditions

摘要

In the present study, molecular dynamics simulation was used to investigate the influence of amorphous intergranular films (AIF) and its thickness on possible crack retardation in nanocrystalline Cu under tensile and cyclic loading conditions. Structural analyses were carried out based on different methods such as centro symmetry parameter, common neighbor analysis, and atomic strain. Results showed that specimens with AIF thickness as small as 0.5 nm can restrict the propagation of both perpendicular and parallel cracks during uniaxial tensile deformation. By increasing the AIF thickness, the crack propagation was found to be further retarded due to crack tip blunting. Atomic strain analysis also revealed that thicker AIF localized the strain distribution more strongly thus inhibiting the nucleation of multiple intergranular cracks and subsequent rapid fracture. In case of cyclic loading, the strain was accumulated through the formation of twins/stacking faults when the AIF thickness was 0.5 and 1 nm, which can interact with the AIF and eventually cause the nucleation of voids/cracks. However, increasing the AIF thickness to 2 nm can restrict such mechanism as the strain was mostly accommodated by the amorphous phase.