Effect of sheet thickness on the FSW parameters for dissimilar aluminium grades tailor welded blanks

Friction stir welding has been in use since 1991, for various applications in aerospace, automotive, shipbuilding industries, especially in fabrication with aluminium alloys for structural members. The friction generated between the rotating tool and blank material heats up the base metal, when it is deformed, stirred and mixed. As this takes place in solid state, dissimilar materials are joined with relative ease. This paper describes an attempt to create a joint between AL5083 and AL6082 with optimal friction stir welding parameters and determine the mechanical behaviour of the tailor welded blank for automotive and structural use. The former is non-heat treatable alloy and the latter is treatable aluminium alloy. Thickness of the blanks is varied between 1 and 3 mm to create dissimilar joints and its influence on the joint properties are studied. The process parameters, including tool rotation speed, traverse speed and the applied axial force, were varied to form several dissimilar joints. An empirical relation to predict the tensile strength of the joint is established along with optimal FSW process parameters to attain maximum joint strength. The relationship between optimal FSW process parameters and the sheet thickness is also found out.