Evaluation of dissimilar metal joining of aluminum alloy to stainless steel using the filler metals with a high-entropy design

Fe-Al intermetallic compounds (IMCs) have huge adverse effects on the dissimilar metal joining of aluminum to steel. High-entropy alloys can use high mixing entropy to promote the formation of single-phase solid solution structures, which would have significant advantages in inhibiting the formation of Fe-Al IMCs in the welding of Al/steel joints. In this study, three types of filler metals, including CoZnCuMn0.8Si0.2 powders with a high-entropy design, the FeCoCrNiMn high-entropy alloy powders, and the comparative Al-12Si powders, were used to join the dissimilar metals between Al 6061 alloy and 304 stainless steel by laser deposition welding. It was found that high-entropy filler metals, including CoZnCuMn0.8Si0.2 and FeCoCrNiMn powders, could successfully be used to join dissimilar metals of aluminum to steel. The high-entropy effect could be achieved in the weld zones (WZs) by using CoZnCuMn0.8Si0.2 and FeCoCrNiMn powders, which could significantly inhibit the formation of Fe-Al IMCs in the WZs, and promote the formation of fine and equiaxed grains, without element segregation, in the WZs. An unmixed zone with a width of 10-20 mu m was formed between the WZ and HAZ in the Al 6061 alloy side for those two dissimilar joints. And some Fe-Al IMCs with submicron or nanoscale size were presented in the unmixed zones.