Effects of orientation on fatigue crack propagation of Ni3Al under super-gravity by molecular dynamics simulation

Abstract

The effects of orientation on fatigue crack propagation of Ni3Al alloys under the super-gravity condition were studied by using the molecular dynamics method. The research found that the crack initiation and propagation mechanisms were different for different orientation crack models: the [001](010) crack germinated in the form of blunting damage and voids and the [1̄10](110) crack began initiation as blunting damage and slip bands. For the [112̄](111) crack, the initiation mechanisms of the crack were the same as the [1̄10](110) crack. In the crack propagation stage, the main deformation mechanisms of all crack models were slip bands, but the slip directions were different: the [001](010) crack and [112̄](111) crack presented ductile cracking and the [1̄10](110) crack presented brittleness fracture. Then, the crack growth rate and stress intensity factor were also analyzed under the super-gravity condition. The results showed that the [112̄](111) crack had the slowest growth rate compared to other two cracks under the super-gravity condition, and the [112̄](111) crack had the maximum stress intensity factor variable at initiation, but the variation tendency of stress intensity factors was slowest for the [112̄](111) crack under the super-gravity condition.