This study explores the use of acoustic emission (AE) signals for in situ characterization of recrystallization during laser processing. With millisecond-scale temporal resolution, AE monitoring can detect critical events during the recrystallization processes, including dislocation reorganization, nucleation, and grain growth. To connect such AE signals to recrystallization events, simultaneous in situ X-ray diffraction measurements were performed to establish a ground truth that could be correlated to collected AE data. From these experiments, a dominant frequency related to recrystallization was identified at ∼ 188 kHz using the current experimental setup. This frequency was isolated by filtering the raw AE data via a combination of power spectrum density distribution analysis, harmonic identification, and empirical mode decomposition. Focusing on the AE data from this frequency, it was possible to identify critical events during recrystallization, including the onset of nucleation as well as the completion of the recrystallization process. These findings represent the first attempt to unveil the acoustic signature of recrystallization, demonstrating the potential for real-time monitoring and control of diffusive microstructural evolutions during rapid processing. They further suggest that AE monitoring can serve as a powerful tool to optimize laser processing and enable precise microstructure control during recrystallization.
Navarre et al. (Thu,) studied this question.