Avalanche-Like Dynamics of Indentation-Induced Plastic Deformation in AZ31 Revealed by Acoustic Emission

Indentation-induced plastic deformation in the AZ31 alloy was investigated via analysis of acoustic emission (AE) signals. By the Kaiser effect and statistical analysis of amplitudes on the basis of Shannon entropy, an efficient method to single out the signals reflecting plastic deformation has been proposed. Further analysis of the obtained signals revealed power-law scaling between the probability distribution density and the amplitude, duration, and energy. The results demonstrate that dislocations induced by macro-indentation also follow the avalanche-like dynamics and the self-organized criticality features as those induced by nanoindentation, which cannot be observed only from the indentation force versus displacement curves. The median frequency of the acoustic emission signals has also been found to be correlated with the strain hardening rate of the AZ31 alloy. Suspected detwinning signals are also observed during the unloading process. The results may help better understand the plastic deformation in the alloy and render the indentation technique a more powerful tool for characterizing mechanical properties.