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 2.78mm/year. The precipitation of 14H lamellas within alpha-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. (C) 2020 Published by Elsevier B.V. on behalf of Chongqing University.