Material flow velocity, strain and strain rate in ultrasonic vibration enhanced friction stir welding of dissimilar Al/Mg alloys

Abstract

Friction stir welding (FSW) and ultrasonic vibration enhanced FSW (UVeFSW) of dissimilar Al/Mg alloys were conducted to elucidate the effect of ultrasonic vibration on the main process variables like material flow velocity, strain and strain rate. 1060 aluminum foils as the marker material were embedded respectively in the Mg on the advancing side and the Al on the retreating side, and the deformation of the aluminum foil at different positions was measured on the horizontal cross-section of metallographs after welding. The principles of mass conservation and plane strain were applied to obtain the flow velocity, strain and strain rate of the marker material around the tool in FSW and UVeFSW. The ultrasonic vibration induced increases in the material flow velocity, strain and strain rate in front of the tool were experimentally determined. Such measured results of the process variables lay solid foundation to reveal the UVeFSW process mechanism of joining dissimilar Al/Mg alloys.