Effects of ultrasonic vibration in the CMT process on welded joints of Al alloy

An ultrasonic peening device was used to supply ultrasonic vibration during cold metal transfer welding of Al alloys. Application of ultrasonic vibration was found to increase the weld depth and weld reinforcement and to decrease the contact angle. The Al-Si eutectic lamellar spacing increased and the pore number decreased. There were many fine equiaxed grains near rich Al-Si eutectic structures. A grain size range of 50-500 nm was obtained through grain refining brought about by cavitation and acoustic streaming. This grain refining led to the increment of hardness and wear resistance.