Mechanical and corrosion behavior of low-alloyed Mg-1Zn-1Zr-xSn (x = 1, 2, 3, 4, 5) alloy prepared by powder-in-tube rolling (PTR)

Magnesium (Mg) alloys have unique biodegradable property with low density, non-toxicity, and mechanical properties that are similar to human bones attracting many biomedical applications from bone to cardiovascular implants. The combination of mechanical strength and degradability of Mg makes it suitable for bone fixation. Rapid degradation rate of Mg, however, is very challenging and prevents the widespread use of the implants. Trace amounts of Zn contribute to Mg strength by a process of solid solution strengthening, and then refined effectively by Zr. The addition of Sn to Mg alloys could enhance mechanical and corrosion properties by forming Mg ₂ Sn phase. The difference in melting points of the elements and easy oxidation make low-alloyed Mg alloys hard to control alloying compositions during casting process. The objectives of the current research were to study the effect of Sn addition on mechanical and corrosion properties along with its effect on hydrogen evolution rate of Mg-1Zn-1Zr-xSn (x = 1, 2, 3, 4, 5) alloys prepared by Powder in Tube Rolling (PTR) method. In this research, quaternary Mg-1Zn-1Zr-xSn (x = 1, 2, 3, 4, 5) alloys were manufactured by PTR method. Steel tube was used in order to hold the powder during the rolling process and to further prevent the oxidation of Mg during sintering process. The PTR treated Mg alloys reached 98.3% of theoretical density. There were several porosities observed on the surface of the PTR specimen even with high density. The hardness value increased as the amount of Sn addition increased. SEM and XRD observation revealed that there are two main intermetallic phases emerging on the surface of the alloys, which are Mg ₂ Sn and Zn ₂ Zr ₃ . The intensity of Mg ₂ Sn increased as the amount of Sn increased as well as Zn ₂ Zr ₃ reached its maximum intensity when the addition of Sn was 5 wt.%. The observed Mg ₂ Sn intermetallic phase was distributed along the grain boundaries, while Zn ₂ Zr ₃ particles diffused inside Mg matrix. The degradation behavior of the alloys was evaluated by potentiodynamic polarization test (PDP) in SBF solution at temperature of 37±1°C. The addition of Sn simply shifts the corrosion potential towards positive zone and lowered the corrosion current density. More Sn was added to alloys, the corrosion potential was in negative zone and corrosion current were increased.