Acoustic profiling of intermittent plasticity

Unraveling the complexities of metal deformation requires a deep understanding of dislocation dynamics and their intermittent behavior. Here, high-resolution acoustic emission (AE) measurements during in situ microcompression of Ni single-crystal micropillars are used to reveal new insights into the rapid deformation dynamics of dislocation avalanches. Spectral analysis of the AE signals uncovers multiple short waves during individual strain bursts, exposing a rich landscape of intermittent plasticity that was previously hidden. Our analysis identifies distinct acoustic signatures that correlate with various stages of deformation: early-stage large avalanches generate strong AE bursts, while later stages characterized by denser dislocation networks emit AE signals of lower amplitude. Notably, given the used sensor, a consistent AE frequency band ranging from 30 to 50 kHz is observed across all recorded avalanches, directly linking this spectral feature to the kinematics of dislocations moving through the crystal lattice. These findings provide a non-destructive characterization approach of dislocation dynamics during the deformation of bulk metals and establish quantitative connections between defect dynamics and macroscopic deformation behavior. More broadly, this work highlights the potential for AE-based techniques to provide insights into the fundamental mechanisms of plasticity in crystalline materials.