Effect of magnesium content on the high temperature adhesion of Al–Mg alloys to steel surfaces

The transfer and adhesion of material to die surfaces during the rolling or stamping of aluminum alloy sheets reduce the surface quality of the finished product, particularly when these operations are conducted at elevated temperatures. This study investigates the effect of magnesium content on high-temperature adhesion between aluminum alloys containing different percentages of magnesium, and an AISI 52100 steel. 5000 series aluminum alloys with magnesium contents ranging to 4.7 wt.% were tested using a pin-on-disc configuration under a normal force of 0.5 N at 713 K, establishing an adhesive junction with the steel counterface. The tangential force required to break this junction (the junction strength) was measured. The junction strength of 99.99 purity aluminum was 0.69 ± 0.03 N. The junction strength decreased in alloys that featured a higher magnesium content, with the 4.7 wt.% Mg alloy displaying the lowest strength of 0.36 ±0.03 N. Magnesium diffusion to the surface during heating formed a magnesium-rich layer, with thicker layers appearing in alloys with high magnesium content. These layers decreased the junction strength and reduced adhesion between the Al-Mg alloy and the steel.