Scaling Effects in Reversible Microplastic Strain

Experimental studies of the non-linear internal friction is an efficient tool to derive reversible (microplastic or anelastic) dislocation or twin-related strain as a function of stress amplitude or temperature. We analyze here the anelastic behaviour (both dislocation and twin boundary related) of different crystalline solids based on the non-linear internal friction data obtained by different techniques. We give experimental evidence that the microplastic reversible strain is heterogeneous in space and intermittent in time, just like its macroscopic irreversible counterpart. It is shown that the stress - anelastic strain response for different materials can demonstrate both a scale-free power law (jamming-like dynamics) and typical depinning critical behaviour. We found that in the case of jamming-like dynamics, the stress exponent can vary substantially for the dislocation microplastic strain in different crystals, but is universal for microplastic strain related to twin boundary motion in a variety of martensitic structures.