Influence of Re on the propagation of a Ni/Ni3 Al interface crack by molecular dynamics simulation

The influence of Re on the propagation of a (0 10)[1 0 1] crack in the Ni/Ni3Al interface, including crack propagation velocity, crack-tip shape, and dislocation emission, is investigated using a molecular dynamics method with a Ni-Al-Re embedded-atom-method potential. The propagation velocity of the crack noticeably decreases at 5 K when 3 or 6 at% Re atoms are added into the Ni matrix. At 1033 K, the crack tip becomes blunter and emission of dislocations becomes easier with Re addition, owing to the larger bond strength between Re and Ni atoms. Furthermore, we calculate the unstable stacking energy (gamma(us)), surface energy (gamma(s)), and adhesion work (W-ad) of the interface. When Re atoms are randomly doped into a Ni matrix, gamma(s)/gamma(us) increases correspondingly. This means that Re addition decreases brittleness and improves ductility. The calculation also shows that gamma(us) is not affected by Re-Ni atomic interaction, and that Re-Re atomic interaction has some effect on gamma(us). In addition, Wad increases with Re addition, and a small increase in W-ad results in a larger decrease in crack velocity. This indicates that Re-Ni atomic interaction restrains crack propagation velocity at low temperature.