Dislocation activity in aluminum at ultra-high strain rates: Atomistic investigation and continuum modeling

[Display omitted] •Dislocation transonic transition is registered in aluminum with MD.•Nucleation of secondary dislocation in local stresses of initial dislocation is observed.•Equation of dislocation motion is calibrated for sub- and transonic regimes.•Model of secondary dislocation nucleation in sub- and transonic regimes is proposed. The work examines the features of plastic relaxation in an aluminum single crystal containing an edge dislocation, deformed at a shear strain rate of 0.85–3.35ns−1. An atomistic study shows that at shear strain rates up to 1.13 ns−1, the dislocation slips in the subsonic regime usually assumed for aluminum, with an upper speed limit equal to the transverse sound speed. At a shear strain rate of 2.55ns−1 or higher, after a short movement with velocity limited by the transverse sound speed, the dislocation undergoes into the transonic regime, when its velocity is limited by the longitudinal sound speed. In all the cases considered, the rate of plastic relaxation provided by the slip of single initially existing dislocation is insufficient to relax the shear stress in the system. The strain increase in the system leads to the nucleation of secondary dislocations near the initially existing one. The nucleation of secondary dislocations always occurred in the local stress field created by the initially existing and moving dislocation. The nucleation of secondary dislocations in the subsonic and transonic regimes differs due to the change of the local stress field of the moving dislocation. A simple continuum model of stress relaxation is proposed that describes the observed features of the motion and nucleation of dislocations. The model is parameterized using the automatic Bayesian parameter identification. The parameters determined in this way are in reasonable agreement with the values known in the literature.