Multi-response Optimization and Mechanical Behaviour of Al–Cu/Al–Mg–Si Alloys by Dissimilar Friction Stir Welding

Abstract

AA2024 (Al–Cu alloy) and AA6061 (Al–Mg–Si alloy) are joined by friction stir welding (FSW) technique. The process parameters are selected using Taguchi L9 orthogonal array and optimization was carried out in two modes, namely single response by ANOVA and multi-response by grey relational analysis (GRA). ANOVA results revealed that rotational speed has the maximum influence on ultimate tensile strength (UTS) and yield strength (YS), whereas traverse speed dominates in percentage elongation and impact strength. The weld trial with parameter 60 mm/min, 1000 rpm and threaded shoulder is found to be optimal through GRA with the responses such as 221 MPa ultimate tensile strength, 184 MPa yield strength, 15.1% elongation and 7.86 J impact strength. The validation of predicted and experimental response shows very minimal error of 2%. The microstructural study reveals finer grains in the weld nugget and formation of an onion ring. The tensile studies indicated the failure of welded joints at the heat affected zone of AA6061 alloy which is further confirmed by hardness studies.