Localized Corrosion of Hypoeutectic Aluminum-Magnesium Alloys and the Effect of Secondary Phases

摘要

Alloys F3K (A 339) and F3S (A 359) with and without SiC reinforcement wererninvestigated to observe their susceptibility to localized corrosion and the interrelationshiprnbetween their microstructure and localized corrosion. Both alloys showrna substantial increase in the yield strength and tensile strength on introduction of 20rnvol % reinforcement. Alloy F3K (A 339) contain mainly precipitate of NiAl3, Mg2Sirnand CuAl2 and alloy F3S (A 359) precipitates of Mg2Si. These precipitates arernpopulated densely at the SiC/Al matrix interface and are preferred sites for localizedrncorrosion. The unreinforced alloys show a higher corrosion resistance than theirrnreinforced counter parts and alloy F3K-20S (A 339) shows a lower resistance tornlocalized corrosion than alloys F3S-20S (A 359) because of the presence of a largerrnnumber of intermetallic compounds. The investigation proved that silicon carbide/Alrnmatrix interface is highly reactive to localized corrosion because of its highrnpopulation of intermetallic compounds. These findings contribute to a betterrnunderstanding of the mechanism of localized corrosion in aluminum metal matrixrncomposites reinforced with silicon carbide.