Microstructure characterization and corrosion behavior of Mg–Y–Zn alloys with different long period stacking ordered structures

Mg–Y–Zn alloys with long period stacking ordered (LPSO) structure have received much attention recently and exhibit great potential in applications such as automotive, aerospace and in bio-medical fields. This paper aimed to investigate the effect of different phase constitution of LPSO structures on corrosion rate of bio-medical Mg–Y–Zn alloys. The results showed that as-cast Mg98.5Y1Zn0.5 alloys containing only 18R structure exhibited the highest corrosion resistance with the corrosion rate of 2.78 mm/year. The precipitation of 14H lamellas within α-Mg grains during solid solution treatment introduced the crystallographic orientation corrosion by accelerating micro-galvanic corrosion. The increase of 18R/14H interfaces deteriorated the corrosion resistance, and the grain boundaries also suffered from severe electrochemical dissolution. This work suggested that Mg–Y–Zn alloys with single LPSO structure (either 18R or 14H) exhibited better corrosion resistance than alloys with co-existence 18R and 14H LPSO structures.