Effect of Scandium and Zirconium on Mechanical and Exfoliation Corrosion Properties of Al-Mg-Mn Alloys

To quest for the best combination of mechanical properties and exfoliation corrosion resisting property of Al-Mg-Mn base alloys, and to seek after the effect of Sc and Zr on mechanical and exfoliation corrosion properties of Al-Mg-Mn alloys, comparative research technique was used, the mechanical properties of Al-Mg-Mn alloys with and without minor Sc and Zr treated by different annealing were measured, the degrees of exfoliation corrosion for these alloys through accelerated exfoliation corrosion test were evaluated, and polarization curves of these alloys were measured, too. The micro-morphologies of corrosion specimens were observed by SEM and the corrosion product was analyzed using EDS. Optical microscope and TEM were used, the relationship between their microstruc-tures and mechanical properties, exfoliation corrosion resisting property was investigated, and the results show that the addition of minor Sc and Zr can enhance the strength greatly and also improve the combination of strength and plasticity. Moreover, the addition of minor Sc, Zr does not cause appreciable decrease of exfoliation corrosion resisting property, the Al-Mg-Mn-Sc-Zr alloy annealed at 350 ℃ for 1 h has excellent combination of mechanical properties and exfoliation corrosion resisting property, the satisfied combination of mechanical properties nad exfoliation corrosion resisting property can be obtained by means of adding minor Sc and Zr, decreasing the content of Mn, and adopting reasonable annealing practice.

Effect of Scandium and Zirconium on Mechanical and Exfoliation Corrosion Properties of Al-Mg-Mn Alloys