Interatomic potentials and dislocation simulation for the ternary B2 Ni-35A1–12Fe alloy

Interatomic potentials of the embedded atom type were developed for the Fe-Ni-Al system. The Fe-Ni pair potential was obtained by empirical fitting to the properties of FCC Fe-Ni alloys. The Fe-Al and Ni-Al potentials required for the ternary simulations were derived in our previous work from lattice and elastic properties of B2 FeAl and NiAl. The Fe-Ni potentials predict the stability of the Fe-Ni FCC disordered equiatomic phase with respect to the L10 and BCC phases. Shear fault energies along the {110} type planes in FeAl were computed showing stable planar faults deviated from the exact APB fault. Core structures were simulated for the (100) dislocations. These dislocations dissociate into superpartials that were not exactly of the 1/2(111) type but 1/8(334) in agreement with the calculated stable planar fault for {110} planes. The ternary potentials were used for the simulation the B2 ternary alloy Ni-35Al-12Fe. The (100) screw dislocation was simulated in Ni-35Al-12Fe for comparison with the previously reported results on the same dislocation in NiAl and FeAl. This study shows that the behavior of the (100) screw dislocation in the ternary alloy can be considered as an intermediate between NiAl and FeAl. The dislocation always dissociates into two superpartials along a {110} plane as observed in FeAl. However, the distance between these superpartials depends on the actual distribution of the atoms in the simulation. The separation distances computed range from a complete dissociation, as in FeAl, to a very closely dissociated configuration more similar to that in NiAl. This suggests an important interaction between the dislocation and point defects present in the structure. The superpartials appeared to be highly mobile along the {110} plane in order to reach energetically stable regions within the crystal.