The mechanisms of nucleation, thickening and growth of crystallographic slip bands were studied, from the sub-nanoscale to the microscale, by using three-dimensional dislocation dynamics. In the simulations, a single face-centered cubic crystal was strained along the [111] direction at three different strain-rates: 104, 105 and 106/s. Dislocation inertia and drag were included, and the simulations were conducted with and without cross-slip. With cross-slip, slip-bands formed parallel to active (111) planes as a result of double cross-slip onto fresh glide planes within localized regions of the crystal. In this manner, fine nanoscale slip bands nucleated throughout the crystal and, with further straining, built up into larger bands by a proposed self-replicating mechanism. It was shown that slip bands were regions of concentrated glide, high dislocation multiplication rates and high dislocation velocities. Cross-slip increased in activity in proportion to the product of the total dislocation density and the square root of the applied stress. The effects of cross-slip upon work-hardening were attributed to the effect of cross-slip upon mobile dislocation generation, rather than slip-band formation. A new dislocation-density evolution law was presented, for high rates, which introduced the concept of the mobile density; a state variable that was missing from most constitutive laws.

Slip Band Formation and Mobile Dislocation Density Generation in High Rate Deformation of Single FCC Crystals. Z.Q.Wang, I.J.Beyerlein, R.LeSar: Philosophical Magazine, 2008, 88[9], 1321-43