Effect of Cu addition on the mechanical properties and corrosion behaviours of Al–9.2Mg–0.8Mn alloy

Microalloying is an effective method to improve the properties of Al–Mg alloys. The microstructure, mechanical properties and corrosion behaviours of Al–9.2Mg–0.8Mn– xCu ( x = 0–1.2 wt-%) alloys are studied to promote the application of Al–Mg alloys. The addition of Cu increases the strength of the alloy, where the ultimate tensile strength of 0.6 wt-% Cu alloy is improved by 43 MPa. Moreover, the addition of Cu significantly affects the corrosion behaviours of alloys. For as-sensitised alloys, compared to the matrix, the 0.1 wt-% Cu alloy shows a 28.3% reduction in pitting corrosion mass loss, which is attributed to the Cu element can form a stable passivation film, and the 0.3 wt-% Cu alloy shows a 15% reduction in intergranular corrosion mass loss, which is attributed to the addition of Cu can restrict the β phase precipitation at grain boundaries. The study shows that Cu-alloying can improve the comprehensive properties of Al–9.2Mg–0.8Mn alloys.