Improving the mechanical properties and biocorrosion resistance of extruded Mg-Zn-Ca-Mn alloy through hot deformation

Mg-Zn-Ca-Mn alloys have been developed due to their great potential as new generation of biomaterials while thermo-mechanical processes can promote its mechanical and corrosion properties. In this study, effect of hot deformation parameters such as temperature and strain rate on mechanical behavior and corrosion properties of Mg-4Zn-0.5Ca-0.75Mn alloy was investigated. Therefore, hot extrusion process at 450 degrees C with ratio of 12:1 and hot deformation tests at various conditions (300-450 degrees C and 0.001-1 s(-1)) were carried out to refine the grain size and improve both mechanical and corrosion properties of Mg-Zn-Ca-Mn alloy. Electrochemical tests were carried out in simulated body fluid (SBF) solution at room temperature using Ivium-n-Scat. The microstructural results and flow curves showed the fine grain microstructure and twinning-free grains as well as fully recrystallized grains achieved at 350 degrees C and 400 degrees C at lower strain rates. Also, polarization curves indicated that the corrosion potential shifts toward more noble potential by increasing the temperature parameter. The corrosion rate decreased from 0.31 to 0.12 mm/year at 400 degrees C and 0.001 s(-1) due to the fine grain microstructure. Indeed, the protective passive film covered the grain boundaries surface which decreases the corrosion rate and retards the breakdown of passive film and pitting corrosion. Fine grain and fully recrystallized microstructure through hot compression test at 400 degrees C of Mg-Zn-Ca-Mn alloy provided a great potential for biomedical application owing to the combination of both improved mechanical properties and enhanced corrosion resistance. Finally, the lowest corrosion rate of the Mg-Zn-Ca-Mn alloy was obtained at 400 degrees C which is nearly similar with the coated samples and Mg alloys reinforced with hydroxyapatite.