Nonequilibrium thermodynamics, kinetics, and self-organization of dislocation avalanche plasticity

• The description of dislocation avalanching is described in the context of a Gibbs thermodynamic description of the constrained local equilibrium state of each subsystem forming the basis of the precursor dislocation-barrier reaction probability. • Avalanching is triggered by precursor dislocation segment reactions, with the power-law regime of avalanching corresponding to a plateau of degree-of-correlation of dislocation-barrier reactions that reflects a second order phase transition, first a jamming transition followed by a depinning transition. The degree-of-correlation of reactions is an important novel aspect of this framework. • Scale-free intermittent flow with universal scaling up to some maximum avalanche size is realized only in the depinning transition, with the jamming transition expressing dislocation and subsystem configuration dependent scaling exponents. • Decorrelated reactions invite spatio-temporal overlap of avalanches, delaying early stage jamming transition and leading to strain rate dependent behavior of the stress-integrated cumulative size distribution of avalanches and transient behavior often observed in small laboratory specimens. • Statistical inhomogeneity of heterogenous obstacles and dislocation sources confer more pronounced wild avalanche strain bursts to behavior of micron scale specimens. • Specific identification and linkage of the avalanche power-law scaling characteristics to kinetics of thermally activated precursor reactions are discussed for FCC, BCC and HCP crystals along with the role of decorrelated reactions, including multiplication and cross-slip. Representative experimental findings are reviewed regarding the distribution of avalanche sizes in crystals. Insight gained from mean field theory regarding universal scaling relations in the depinning transition and the influence of the dislocation jamming transition on extended criticality are addressed within a framework for nonequilibrium thermodynamics for a sequence of constrained local equilibrium states introduced by ( McDowell 2024a , b , c ) and McDowell and Liu (2025) . The concept of the degree-of-correlation of dislocation-barrier reactions plays a central role. Early-stage decorrelated dislocation multiplication processes along with cross-slip and other weak barrier reactions are argued to diminish in the jamming transition as internal stress fields develop in an extended critical state towards the depinning transition. Under depinning dominance universal scaling is realized. The progression towards increasingly correlated reactions is argued to maximize the entropy of pending reactions at each step along the nonequilibrium trajectory as a proxy assertion for maximal intrinsic entropy production associated with state transitions. In the depinning transition, dislocation avalanches of all sizes up to the maximum avalanche size established by the dissipation-weighted effective enthalpy barrier contribute to slip system shearing. Size effects and “wild to mild” transitions from submicron specimen responses up to polycrystals are interpreted in terms of scale-appropriate dislocation precursor reactions and averaging of distributed avalanching processes. Dominant effects of free surface interactions and dislocation source limitations are exerted for specimens with size below 1 μm, with jerky avalanching owing to statistical inhomogeneity and elevated stress. Increasing specimen size leads to progressive smoothing of overall stress-strain response.