The Mechanism Behind the Oxidation Protection of High Mg Al Alloys with Beryllium

Abstract

The addition of beryllium to Al-Mg alloys is known to cause a dramatic decrease in oxidation; however, the mechanism behind this protective effect is not yet fully understood. To aid in finding an alternative to the toxic Be, a fundamental study of Be additions has been carried out. Industrial samples containing 2 ppm Be and a model alloy with 100 ppm Be were oxidized at temperatures between 550 °C and 750 °C in a horizontal tube furnace. The oxide layer and oxide–metal interface were investigated using SEM, FIB, and XPS. It was found that Be forms a uniform oxide layer at the oxide–metal interface which slows the diffusion of Mg and Al from the metal into the oxide layer resulting in a reduced oxidation rate and an increase in the time for breakaway oxidation to occur.