Tunable mechanical and degradation properties of biodegradable Mg-Y-Zn alloys via Zn content regulation

This study aims to explore the effect of Zn content on mechanical properties and degradation behaviour of biodegradable Mg-Y-Zn (WZ) alloys via mechanical and in-vitro testing. Microstructure characterization showed that the morphology and composition of the secondary phases changed significantly with the increase of Zn content. The continuous precipitation of long-period stacking ordered (LPSO) phase led to an increase in the strength of the WZ alloys. However, the corrosion resistance of the WZ alloys increased initially and then decreased as Zn content increased. In the Mg-9.1Y-1.8Zn (WZ92) alloy, the continuous rod-like LPSO phases formed an effective degradation barrier to prevent the corrosion penetration, thus leading to a uniform and slow degradation process. Discontinuous and dispersed (i.e., lamellar-like) LPSO phase existed in the Mg-9.2Y-3.1Zn (WZ93) alloy cannot act as the degradation barrier, and the intragranular fine lamellar structure would aggravate corrosion and promote corrosion penetration into the α-Mg matrix. In addition, the WZ93 alloy with high content of LPSO phase formed more micro-galvanic couples, which exacerbated the micro-galvanic corrosion. EIS results revealed that the WZ92 alloy exhibited better corrosion resistance due to the formation of a more stable and thicker surface film. This study demonstrates that the Mg-Y-Zn alloy with tunable mechanical and degradation properties can be fabricated efficiently and economically by regulating the Zn content, and is expected to be a promising candidate in the field of degradable medical implant.