Abnormally fast crack propagation induced by short-range ordering in iron-cobalt alloys: A combined experiments and molecular dynamics simulations

Molecular dynamics study on the deformation and fracture of FeCo-based alloys

“…As observable in Figure 5.7, introducing disordering to the alloy reduce the energy barriers that need to be overcome to move dislocations or to create stacking faults within the crystal. Compared to the references, the curve for the ordered alloy aligns well with the FP calculations in the central region, near the γisf [48,114]. The interatomic potential overestimates the energy barriers to develop unstable faults, the increase in γusf and γutf could hinder the movement and slipping of dislocations in the crystal lattice, potentially increasing the stability of the B2 structure and the subequent brittleness of the alloy as observed in further sections.…”

“…This can be considered the first MD attempt to study the deformation mechanics of FeCo, but due to the nature of the EAM, this potential cannot be extended to describe other Fe-Co based systems such as FeCo-V. Subsequently, Li et al [48] Relying on the MEAM, Choi et al [49] developed different binary potentials, including Fe-Co, aiming to merge them to describe a multicomponent system. The potential demonstrated a good capability to reproduce FeCo basic properties such as the energies of formation and elastic constants with good agreement with first principles calculations, correctly reproducing the stability of the low temperature phases, namely the ordered B2 and the disordered bcc.…”

“…As can be observed in Figure 5.6, the introduction of disorder reduces the GBs energies, which should in turn provide a higher ductility. structural configuration of the B2 in the evaluated slip systems, γisf is equivalent to the APB energy [48,114]. As observable in Figure 5.7, introducing disordering to the alloy reduce the energy barriers that need to be overcome to move dislocations or to create stacking faults within the crystal.…”

“…Using the same methodology, we also computed the generalized stacking fault energy (GSFE) curves, varying the distances relative to the Burgers vector. From here the impact of solutes on three important energy values were drawn: the unstable stacking fault energy (γusf), which measures the energy required for temporary lattice defects that can lead to deformation; the intrinsic stacking fault energy (γisf), which is in fact the APB energy in FeCo alloys due to the A2/B2 structure configuration in the studied slip systems [48,114];…”