Analysis of fatigue crack propagation mechanism of Ni3Al under supergravity at atomic size

Mechanisms of fatigue crack propagation of Ni3Al alloy under supergravity are studied by the molecular dynamics method. The initial model of the crack is a [100](010) crack in Ni3Al. Changes in the microstructure evolution, crack growth rate, and stress intensity factor of [100](010) crack are compared and analyzed without and with supergravity. The results show that the deformation mechanisms of the crack tip are slip bands along the a/6[112] direction by dislocation analysis in the absence of supergravity cyclic loading; after adding to supergravity, the mechanisms of crack propagation have changed, multiple voids are formed at the crack tip, and the dislocation lines also grow faster, which cause severe damage to the internal structure of the [100](010) crack in Ni3Al. By tracking the changes in crack length and width, it is found that the supergravity accelerates the growth of crack length and width and reduces the stress intensity factor threshold. Finally, the crack propagation rate increases under supergravity conditions.