An empirical study of CMT-welded interface features and corrosion characteristics of dissimilar joints

Abstract

The goal of this work is to investigate the interface microstructure of the cold metal transfer (CMT) welded dissimilar (AA6061 sheet-galvanized steel sheet) joint at maximum tensile strength (TS) by optimizing the welding parameters using response surface methodology. To attain maximum strength, CMT process variables like voltage (V), current (I), and wire feed rate (WFR) are used to rotate against the output response. The optimized dissimilar joint exhibited a sound appearance without any visible defects and better TS of 141 Mpa as the voltage of 13.9 volts, current of 100 amps, and WFR of 6.2 m/min was given as input. Furthermore, the third intermetallic compound formed at the weld interface at optimized conditions due to controlled heat input was found to be well-controlled and less than 9 um. The weld interface and base metal on the aluminium side of the joints fabricated under various conditions showed larger grains than on the steel side. In addition, the optimized joint was performed to evaluate the corrosion rate, and the results showed 6.8 µA/cm². The fracture morphology of the joint reveals that the Fe₂Al₅ compound layer on the aluminium WZ was where joint fractures were most often seen. The aluminium particles on the steel side were found to be unaffected and were observed in the majority of the dissimilar joints at the WZ owing to the intact bonding between the aluminium particles and steel matrix.