Determination of Microstructure of Friction Stir Welded Joint for Aluminium Alloy 6351 (He-30)

Abstract

The FSW process involves the translation of a rotating cylindrical tool along the interface between two plates.  The weld is formed by the deformation of the material at temperatures below the melting temperature. The welding parameters such as tool rotational speed, welding speed, axial force etc., and the tool pin profile plays a major role in deciding the weld quality.  The main aim of this thesis is to investigate metallurgical properties of friction stir welded aluminium alloy 6351 (HE-30).  Heat treatment improves microstructure. Tapered cylindrical tool pin profile shows fine grains at weld centre.  The micro structure shows the fine grains at the weld centre in Tapered cylindrical tool with heat treatment for air cooling.  In case of triangular tool the grains are coarse at the weld region and bond integrity is poor.  In case of square tool, due to sharp edges the speed tool is reduced in the metal, so that low temperatures are generated.