Effect of Re on dislocation nucleation from crack tip in Ni by atomistic simulation

Effects of Re, W and Co on dislocation nucleation at the crack tip in the γ -phase of Ni-based single-crystal superalloys by atomistic simulation

“…The sum of energy difference of atom j between the saddle state and the initial state gives the energy difference between the saddle state and the initial state of the system. The relations are given as follows [6]: normalΔ E j=E jsad−E jiniand normalΔ Eact=∑ j=1NnormalΔ E j,where equation (3.1) gives the energy difference of atom j between the saddle state and the initial state, E jsad and E jini denote the energy of the atom j in the saddle state and the initial state, respectively. N is the number of atoms in the system.…”

“…The Ni–Al–Re, Ni–Al–W, Ni–Al–Co EAM potentials have been applied to predict the physical properties in the respective systems and gave reasonable results [30–32]. In particular, the Ni–Al–Re, Ni–Al–W and Ni–Al–Co EAM potentials have been applied to study the systems containing dislocations or/and cracks [6,23,24,30,33] in the Ni-based superalloys.…”

“…We adopt the false(1 1 1¯false)false[1 1¯ 0false] crack system in Ni under mode I loading, in which the crack lies in the false(1 1 1¯false) plane and the crack front is along the false[1 1¯ 0false] direction. This crack system is chosen as the crack propagation and dislocations nucleation happens easily for this crack system [6,34–36]. This crack system had also been studied by Zhu et al [20] and Liu et al [6] and the models in current research take a similar form as their models.…”

“…This crack system is chosen as the crack propagation and dislocations nucleation happens easily for this crack system [6,34–36]. This crack system had also been studied by Zhu et al [20] and Liu et al [6] and the models in current research take a similar form as their models. To study the alloying effect of Re, W or Co on the dislocation nucleation behaviour at the crack tip, 1 at.% or 2 at.% X (X = Re, W or Co) atoms are randomly doped into the Ni matrix of this crack system.…”

“…The atomistic simulation model is cylindrical with a radius of R = 90 Å and the crack front is along the central (longitudinal) axis as shown in figure 1 a . The crack front contains 29 unit cells in false[1 1¯ 0false] direction (total crack front length is about 72 Å), which is sufficient to obtain an accurate activation energy of an isolated dislocation loop [6,16,20]. As the atomically sharp crack configuration in false(1 1 1¯false)false[1 1¯ 0false] crack system of Ni is unstable, one layer of atoms in the false(1 1 1¯false) plane behind the crack tip is removed to ensure a stable crack tip configuration.…”