Influence of Cooling Rate on Corrosion Resistance of Rapidly Solidified Mg-Zn-Y Alloys with a Long Period Stacking Ordered Phase

摘要

This paper deals with the influence of cooling rate on the corrosion resistance of rapidly solidified (RS) Mg-Zn-Y alloys with a long period stacking ordered (LPSO) phase. To clarify the effect of microstructure modification by rapid solidification on suppressing localized corrosion such as filiform corrosion, several Mg_(97.25)Zn_(0.75)Y_2 (at.%) alloys were prepared with different cooling rates were prepared by the gravity-casting, copper mold injection-casting and melt-spinning techniques. In the alloys solidified at a low cooling rate, filiform corrosion propagated in the early stage of a saltwater immersion test, due to the formation of a massive, block-shaped LPSO phase during casting. In contrast, the alloys solidified at a high cooling rate exhibited excellent corrosion resistance. Rapid solidification brought about grain-refinement and the formation of a supersaturated α-Mg single-phase solid solution, resulting in improved electrochemical homogeneity.