INFLUENCE OF Al CONTENT AND ASSOCIATED β-PHASE MORPHOLOGY ON CORROSION PROPERTIES OF Mg/Al ALLOYS

Abstract

The influence of the Al content and associated βmorphology on the corrosion of Mg alloys has been studied using AZ41 and AZ91series Mg alloys and compared with the corrosion of non Al containing Mg alloy(i.e AZ01). Scanningelectron microscopy (SEM) was used for microstructural examinations. Thecorrosion behaviors were evaluated by immersion tests and potentiodynamicpolarization measurements in 3.5% NaCl solution. The globular shaped βintermetallic phases were present in AZ41 alloy whereas they were transformedinto a more coarsened lamellar or partially divorced β eutectics in AZ91alloys. The resultsshowed that the influence of Al addition on corrosion resistance was morepronounced up to 4 wt% (i.e AZ41) above which its influence was at less extent.The deterioration of the corrosion resistance of the alloys, at higher Alcontents, was attributed to amount and morphology of β (Mg17Al12) intermetallicsand the interruption of continuity of the oxide film on the surface of thealloys owing to coarsened β intermetallics.