Spatiotemporal slip dynamics during deformation of gold micro-crystals

Intermittent plastic deformation in micro-crystals was resolved in both space and time, yielding velocity profiles that peak in a range from approximately 1 μm/s to 100 μm/s. The peak velocities exhibit a broad, close to scale-free distribution, with a scaling regime at high velocities that is compatible with a cubic decay. Slow slip dynamics in the μm/s regime show an approximately flat distribution. An apparent power-law scaling between peak slip-velocity and event size was also observed. The spatiotemporal dynamics of the dislocation-mediated plastic intermittency is discussed in terms of lateral and vertical slip-step growth velocities, where the vertical growth velocity is ∼4 orders of magnitude slower than the lateral dislocation-group velocity, providing a rationale for the measured slow dynamics. In order to validate the experimental results, the response of the used nanoindenter is evaluated for the time during the plastic instability. Fracture tests on Si were conducted to determine the upper bound in dynamic response of the device. Finally, in-situ electrical contact measurements complete the suite of tests that unequivocally demonstrate that the used nanoindentation platform is capable of tracing the spatiotemporal slip dynamics during slip of small-scale crystals.