Dissociation of a<100> edge super-dislocations in Ni3Al, the hardening γ’-phase of Ni-based superalloys, was investigated using molecular dynamics simulations and theory of elasticity. It was shown that these dislocations dissociate either symmetrically or asymmetrically when they were close to the <011> orientation. The symmetric dissociation, called Hirth lock, has the lowest energy. The reasons for the dissociation were the strong energy reduction due to the core splitting and the relaxation of elastic strains within the dissociation area. The dissociation of a<100> edge super-dislocations was the reason for their alignment in <011> orientation in the γ’-rafts of superalloys. However, the dissociation did not block the movement of the dislocation because they penetrate the γ’-rafts by climbing. Under loading conditions, typical for creep tests of Ni-based superalloys at high temperatures (above 1000C), the Hirth lock slightly expands but remained stable. The asymmetric configuration was less stable and could transform into the lower energy Hirth lock.

Dissociation of a <100> Edge Super-Dislocations in the Gamma'-Phase of Nickel-Base Superalloys. Kohler, C., Link, T., Epishin, A.: Philosophical Magazine, 2006, 86[32], 5103-21