Investigations of the sound frequency effect on laser acoustic welding of stainless steel

The key features of laser acoustic welding (LAW) of AISI 321 stainless steel samples are investigated in the paper. It is found that the microstructure and the quality of the welds depend strongly on the frequency of the applied acoustic waves, which were selected at sonic (15 kHz) and ultrasonic (22, 40, 80, and 100 kHz) levels. The impact on the molten alloy acoustic vibrations with a frequency of 80 kHz provides weld joints with a uniform structure without detectable pores and homogeneous chemical composition in the cross-section. This results in noticeable improvements in mechanical properties of the weld. The pronounced displacement of the metal from the melting zone and highly inhomogeneous structure of the weld observed at 15 kHz is attributed to the sonocapillary effect.