Online monitoring of friction stir welding of dissimilar aluminum alloys

Abstract Friction stir welding (FSW) provides an effective solution for joining dissimilar aluminum alloys like AA5083 and AA6061-T6, which are prone to issues like porosity and cracking when welded using conventional fusion methods. This study investigates the use of real-time acoustic emission (AE) monitoring to evaluate weld quality and detect defects such as piping and pinholes during the FSW process. Key AE parameters, including RMS, Hits, Amplitude, Counts, and AE Fast Fourier Transform (FFT) spectra, were examined alongside waveform characteristics. Mechanical testing revealed that defect-free joints achieved a tensile strength of 256 MPa and 82 % joint efficiency, whereas the presence of piping and pinhole defects lowered the strength to 235 MPa and 201 MPa, respectively. Microstructural analysis confirmed the formation of finer grains and higher hardness (93 Hv) in the stir zone of defect-free welds. AE Parametric monitoring showed marked increases in signal intensity in defective welds, especially those with pipping and pinhole defects, validating its potential for defect identification. Shifts in AE FFT spectra peak amplitude frequencies and distinct burst-type waveforms further demonstrated the capability of AE analysis to characterize weld conditions. These findings highlight the effectiveness of AE techniques as a nondestructive, real-time tool for monitoring weld integrity in industrial applications.