Acoustic emission characteristics of micro-discharges in initial pulsed PEO process on 60% SiCp/Al composite

• Published in: Ultrasonics Vol. 138; p. 107213
• Main Authors: Liao, Yizhao, Zhou, Qian, Gao, Chuanli, Li, Hui, Xu, Chi, Jin, Xiaoyue, Du, Jiancheng, Xue, Wenbin, Zhang, Yongzhong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2024
• Subjects: Acoustic emission; Aluminum metal matrix composite; Bubbles; Micro-discharges; Plasma electrolytic oxidation; Acoustic emission; Bubbles; Plasma electrolytic oxidation; Aluminum metal matrix composite; Micro-discharges
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/j.ultras.2023.107213

•AE characteristics of micro-discharges within one pulse period of 6670 μs during PEO process were analyzed by AE technique.•Micro-discharge intensity played a key role in the amplitude and energy of AE signals.•The correlation between AE parameters was analyzed.•AE signals during pulse time mainly resulted from the plasma bubble evolution. The initial discharge process of pulsed plasma electrolytic oxidation (PEO) on the 60% SiCp/2009 aluminum metal matrix composite (Al MMC) in silicate solution was monitored by acoustic emission (AE) technique. Parameters and correlations of AE signals on the Al MMC sample and under water were analyzed, and their generation mechanism was discussed. It was found that the peak amplitudes of AE signals and AE hits during the pulse time quickly increased with the increase of micro-discharge intensity, and the absolute energy of AE signals improved several orders of magnitude. Moreover, different from the peak amplitude, duration and rise time, the duration and count had a strong correlation. Elastic stress waves resulted from the microjet of plasma bubble collapse, the inner-surface friction inside discharge channel, the expansion-shrinkage process of plasma bubbles and micro-crack propagation during rapid solidification of melt are sources of AE signals on the Al MMC sample during the pulse time. However, the expansion-shrinkage process of plasma bubbles plays a key role in the generation of underwater AE signals. In the pause time of one pulse period, the bursting and moving of vapor bubbles result in weak AE signals. It is demonstrated that the AE technique can effectively characterize the features of micro-discharges within a pulse period.