Study on the effect of process parameters in friction stir welding of dissimilar aluminum alloys

Abstract

Friction Stir Welding (FSW) is a recent addition to the solid state newlinejoining processes that has paved way for joining materials that were newlineconsidered difficult to be welded by conventional welding techniques. In this newlineprocess, a cylindrical non-consumable tool, with a profiled probe (pin) newlinerotating about its own axis is slowly plunged into the abutting edges of work newlinepieces rigidly clamped to a backing plate. When the shoulder of the tool newlinetouches work piece surface, the tool is translated (with an axial force) along newlinethe length of the joint forming the joint in the solid state. Aluminum alloys of dissimilar combinations are required to be joined newlinefor many industrial applications. Due to difficulties associated with welding newlinedissimilar aluminum alloys, their usage in practical applications was newlinehindered. Aluminum alloys like Al-Cu (2xxx) and Al- Zn-Mg (7xxx) have newlinepotential application in modern and future aircrafts. For example, the newlineAA7075 plates were friction stir lap welded as skin with the AA2024 newlinestringers in aerospace applications. The tool rotational speed (TRS), welding speed (WS) and tool newlinegeometry are the key operating parameters that predominantly affect the FSW newlineprocess. Successful application of FSW requires proper selection of these key newlineparameters. This study aims to relate the key process parameters of FSW with newlineweld characteristics and also to predict the thermal and mechanical newlinecharacteristics of the weld joint made by FSW through appropriate modeling. newlineResponse surface methodology (RSM) was used to develop a regression model relating mechanical properties and process parameters. The work also newlineaims to develop a physically valid FSW model, based on computational fluid newlinedynamics (CFD) and verifying it by experimental work. newlineFriction stir welding of AA2024 and AA7075 aluminum alloys newlinewas carried out at various TRS, WS and shoulder diameters (SD). Welding newlinetrials were made as per face centered, central composite design, with three newlineparameters and three levels.