Multi-response mathematical model for optimization of process parameters in CMT welding of dissimilar thickness AA6061-T6 and AA6082-T6 alloys using RSM-GRA coupled with PCA

Abstract

The requirement projected by many industries for stronger, lighter, more efficient and cost-effective combined alloys in the welding of two dissimilar materials or dissimilar thickness. The current industry trend is the coalescence of various aluminium alloys of varying thicknesses. In this research paper, Cold Metal Transfer (CMT) welding process was used for the joining of AA6061-T6 and AA6082-T6 using ER4043 filler wire and inspected the effect of different process parameters on mechanical properties of welded butt joints. Current (I), welding speed or travel speed (TS) and gas flow rate (Q) are the input welding process parameters that are to be optimized. Full factorial central composite face-centered design (CCFCD) was utilized to optimize the tensile properties, microhardness and residual stresses. Grey relation analysis (GRA) with PCA is incorporated with CCFCD for finding out the optimal process parameter by considering multi-response parameters simultaneously. ANOVA was executed to interpret the impact of a process parameter on the mechanical properties of the weldments. Results showed that the most dominant process parameter was found to be the welding speed. The optimal process parameter obtained via the GRA-PCA technique is I3-TS1-Q1 (I - 100 A, TS - 5 ​mm/s and Q - 14 ​L/min having heat input 352 ​J/mm) which produces 226 ​MPa of ultimate tensile strength, 12.6% of elongation, 68.7 HV of microhardness and −152.3 ​MPa of compressive residual stress. The desirability of optimality level obtained through CCFD was 65.99% and significantly improved to 97.07 through GRA-PCA.

Keywords

• Cold metal transfer (CMT)
• Central composite face-centered design (CCFCD)
• Grey relation analysis (GRA)
• Principal component analysis (PCA)
• ANOVA and Mechanical properties