OPTIMIZATION OF PROCESS PARAMETERS AND INVESTIGATION ON MICROSTRUCTURAL FEATURES AND FRACTURE SURFACE OF FRICTION STIR WELDED ALUMINIUM ALLOY AA2219

Abstract

Friction stir welding (FSW) is a fairly recent welding technique, invented by The Welding Institute (TWI), Cambridge, and U.K [1]. This technique utilizes a non-consumable rotating welding tool to generate frictional heat and deformation at the welding location, thereby affecting the formation of the joint, while the material is in the solid state [2]. Application areas for FSW include aerospace, ship-building and automotive industry. To date it is with aluminium alloys that FSW is most successfully applied. The reason for pre-dominant use of FSW for aluminium alloys being the combination of process simplicity in principle and wide use of aluminium alloys in many major industries. The Friction stir welding process has a number of process variables which can be broadly categorized into Tool design variables, machine variables and other variables such as the work piece size, work piece properties etc. In order to achieve goals such as maximizing productivity, quality and reproducibility it is necessary to identify and set the optimum level for these variables/parameters. The aim of this research work is to optimize the process parameters for longitudinal seam friction stir welding of aluminium alloy for space launch vehicle propellant tank application. The desired outcome is to obtain a joint that meets the mechanical property requirements and is also free from microscopic defects such as porosities, cracks, lack of fusion etc. This research work also involves a thorough micro structural analysis of the joint cross section and fractures surface studies.