3D misfit potentials dependent deformation behaviors with respect to different dislocation core structures of fcc metals

Dislocations, both screw and nonscrew, in fcc metals are crucial in forming dislocation substructures, significantly influencing deformation mechanisms such as deformation twinning and martensite transformation. In this work, the effects of dislocation types on the deformation behaviors of fcc Al, Cu, and Fe are investigated using the semidiscrete variational Peierls-Nabarro (PN) model. The three-dimensional (3D) misfit potentials are determined from first-principles calculations. The deformation mechanisms and mechanical behaviors are analyzed in terms of variations in the dislocation core structures, along with the PN stress τp and Peierls potential Ep. It is found that the decomposition behaviors of dislocations in fcc metals, as characterized by the stacking fault width, are influenced by the dislocation line angle θ. The interplanar distance Δx perpendicular to the dislocation line, as a function of θ in fcc metals, dominates the magnitude of PN stress τp and Peierls potential Ep. For instance, with Δx decreasing from 3/2 to 1/2, the τp, e.g., for fcc Cu, reduces from 3.20 MPa (screw dislocation) to 0.002 MPa (edge dislocation). The increase of θ is unfavorable to dislocation cross-slip but promotes the occurrence of dislocation climb, deformation twinning, and ϵ-martensite transformation. Consequently, the strain hardening rate can be enhanced in terms of such variations in the deformation behaviors for fcc Al, Cu, and Fe. Our investigations offer an insightful guidance for qualitatively assessing the likelihood and degree of deformation twinning and ϵ-martensite transformation in fcc metals via examining the dislocation core structures.