Effect of solute atoms and Peierls stress on the critical behaviour of dislocations

It is well-known from micropillar and acoustic emission experiments that in crystalline matter plastic strain accumulates in sudden avalanche-like events. Based on the statistical analysis of these bursts it is now apparent that plastic deformation can be described as a critical phenomenon. Whereas the analysis of experiments suggests that scale-free behavior is characteristic only to the onset of yield, discrete dislocation dynamic (DDD) simulations hint at a more involved picture. Namely, the dynamics of the system is of glassy nature, where power-law distributions arise irrespective of the distance to the yielding threshold [1]. These DDD simulations represent pure systems where neither Peierls stress nor any kind of impurities impede dislocation motion.

In the talk we will discuss how linear stability of the dynamics of the system [2] can be employed to reveal internal dynamic correlations between dislocations in a 2D system. We will show that these correlations are long-range in pure systems and become short-ranged in the presence of point-like impurities or a non-zero Peierls stress. The size and scaling of strain bursts are determined by these correlations: bursts get localized and system size independent in the case of impurities, a fact already observed in experiments. These results, thus, shed light on the microscopic origin of internal length scales affecting the statistical properties of the stochastic plastic response.

[1] PD Ispánovity et al, Phys. Rev. Lett. 112, 235501 (2014)
[2] PM Derlet and R Maaß, Phys. Rev. E 94, 033001 (2016)