Analysis of heat and mass transfer in ultrasonic vibration-enhanced friction stir welding of 2195 Al–Li alloy

Abstract

Ultrasonic vibration (UV)-enhanced friction stir welding (UVeFSW) is used for welding of 2195 Al–Li alloy plates. A model is developed to study the heat and mass transfer in UVeFSW of 2195 Al–Li alloy. It reveals that additional UV in FSW could reduce the heat flux and temperature at the contact interfaces when compared to those in conventional FSW. Although the temperature is slightly decreased with additional UV, the acoustoplastic effect of the UV could reduce the flow stress and viscosity in the shear zone, resulting in an enhanced fluidity of the plastic material with a higher flow velocity. It is demonstrated that the variations of viscosity, strain rate and flow stress around the tool at the same radial distance are more severe at low heat input condition, such as with a low rotation speed or a high welding speed. The model is validated by the experimental data.