Effects of Sr addition on microstructure, mechanical and corrosion properties of biodegradable Mg–Zn–Ca alloy

Abstract

Abstract Selection of non-toxic elements existed in human body or certified for tissue regeneration is considered for multifunctional biodegradable metals. The effect of Sr addition on microstructure, mechanical properties, and degradation behavior of biodegradable Mg–2Zn-0.3Ca alloy was studied as an example to gain insight into the Mg–Zn–Ca alloy series. The average grain size of alloys became smaller and more homogeneous distinctly by increasing Sr content. The second phases on the grain boundaries and the interdendritic interstices were also refined with small amount of Sr addition. More concentration of Sr element was detected evidentially at the interface between grains and the second phases. Mg–2Zn-0.3Ca-0.3Sr alloy shows the optimal flexural and compressive strength of (441 ± 18) MPa and (317 ± 13) MPa, respectively. The electrochemical measurement in simulated body fluid showed that addition of Sr would slightly deteriorate the corrosion resistance of Mg–Zn–Ca–Sr alloys. The in-vitro immersion tests were conducted and analyzed in detail by three different immersion stages and got a distinctive corrosion performance compared with the electrochemical measurements. Homogenization annealing was conducted for Mg–2Zn-0.3Ca-0.3Sr alloy, which can reduce dendrite segregation and significantly improve the corrosion resistance of alloy. The degradation process of alloys in simulated body fluid was summarized in detail for Mg–Zn–Ca–Sr alloys. This work not only provides the relationship between microstructure and properties of biodegradable Mg alloys, but also a comprehensive discussion of degradation behavior of Mg–Zn–Ca alloys for orthopedic application.