A Parametric Optimization of FSW Process Using RSM Based Grey Relational Analysis Approach

Abstract

Age-hardenable aluminum alloys, primarily used in the aerospace, automobile and marine industries (2xxx, 6xxx and 7xxx), can be welded using solid-state welding techniques. Friction stir welding is an emerging solid-state welding technique used to join both similar and dissimilar materials. The strength of a friction stir welded joint depends on the joining process parameters. Therefore, a combination of the statistical technique called response surface methodology (RSM) based grey relational analysis (GRA) coupled with entropy measurement technique was proposed to select the process parameters suitable for joining AA 2024 and AA 6061 aluminum alloys via friction stir welding (FSW). The significant process parameters, such as rotational speed (N), welding speed (F), axial load (P) and pin shapes (PS), were considered during the statistical experiment. The results indicate the square (SQ) pin shape plays a vital role and yields an ultimate tensile strength of 141 MPa for an elongation of 12% versus cylinder (CY) and taper (TA) pin profiles. The root cause for joint strength loss and fracture mode was analyzed using scanning electron microscopy (SEM). Severe material flow leads macro defects such as pinholes and porosity degrades the joint strength by approximately 44% for AA 2024 and 51% for AA 6061 fabricated FS-welded aluminum alloys relative to the base material. The results for this approach are useful for accurately controlling the response and optimize the process parameters