Joining Ti6Al4V and AISI 304 through friction stir welding of lap joints: experimental and numerical analysis

Abstract

The results of an experimental and numerical analysis on Friction Stir Welding of dissimilar lap joints made out of AISI304 and Ti-6Al-4 V thin sheets are presented. The mixed joints, welded with varying process parameters, have been characterized from a mechanical and metallurgical point of view. A numerical model able to take into account the behaviour of the two different materials has been used. The numerical results have been utilized to explain the joint properties and the occurring material flow. The effect of the heat input, tilt angle and sheets mutual position has been investigated. It is found that both hooking defects and tunnels may occur with incorrect choice of process parameters. Good nugget integrity is obtained when the titanium sheet is used as upper sheet and high heat input is conferred to the joint. Finally, welding speed influences the nugget morphology as low values contribute to minimize the formation of the hooking defect.