Characterizations of Friction Stir Welding on Aluminum Alloy

The results produced during fluid flow modeling of friction stir welding are described.The viscosity of material in the fully-plasticized region is determined using plunge testing,where the forces that acting on a rotating steel pin as it penetrates the aluminum alloy base material are measured and converted into effective viscosities and temperature output.3-D modeling results show the formation of a chaotic flow zone about 1.5 mm below the tool shoulder.It is suggested that chaotic mixing produces the intermingled lamellae formed in dissimilar FSW welds.Also,transient tool slipp age produced by local liquid formation results in hysteresis in the viscosity/shear stress plane at a critical temperature Tcrit.