The role of aluminium content on the corrosion initiated mechanical failure of AZ series magnesium alloys

Abstract

In AZ series magnesium (Mg) alloys, the percentage of aluminium (Al) influences the quantity and the phase distribution within the magnesium matrix. AZ31 and AZ91 are the widely known alloys in the AZ series which contain 3% and 9% of aluminum (Al) by weight, respectively. Due to the presence of more secondary phase and eutectic regions, AZ91 exhibits higher strength and hardness compared with AZ31 Mg alloy. These secondary phases made of Mg and Al also influence the corrosion behavior in AZ series Mg alloys. Mechanical failure of Mg alloys exposed to corroding environment is influenced by several factors in which the time of exposure is one important element. Therefore, in the current work, both the AZ31 and AZ91 Mg alloys were exposed to corroding environment for different intervals of time (1, 3 and 7 days) and then their mechanical performance has been evaluated. Without corrosion attack, AZ91 has shown superior strength compared with AZ31 Mg alloy. Interestingly, when exposed to corroding environment, AZ91 sample has failed at lower stress values compared with AZ31 sample. The results demonstrated the negative role of Al containing secondary phases on the corrosion initiated mechanical failure of AZ series Mg alloys. It is suggested that for environments with moisture or corroding solvents, AZ91 Mg alloy is more susceptible to corrosion compared with AZ31 Mg alloy.