The Interaction of Point Defects with Stress Fields Generated by Persistent Slip Bands in Face-Centered Cubic Nickel

Using the phase-field modeling approach, the evolution of persistent slip bands (PSBs) in nominally defect-free pure nickel (Ni) single crystals is described. The PSB-matrix model is based on the analysis of steady-state cyclic deformation, involving point defects. The PSBs are regarded as a result of spontaneous evolution of localized dissipative structures in the form of solitary static regions and therefore modeled with eigenstrains. The transport of vacancies accounts for the overall change in dimensions of the PSBs, as the PSB thickens resulting from the outward flux of vacancies. The large vacancy concentration and eigenstrains in the PSB lead to increased stresses at the PSB-matrix interface and subsequent formation of incoherency strains to relieve the stress concentrations. From these observations of the PSB structure evolution and the resulting micromechanical fields, a possible mechanism of local damage at the PSB/matrix interface is observed during cyclic deformation, which can facilitate the formation of a fatigue crack.