Effects of Sr addition on microstructure, mechanical properties and in vitro degradation behavior of as-extruded Zn−Sr binary alloys

The microstructures, mechanical properties and in vitro degradation behavior of as-extruded pure Zn and Zn−xSr (x=0.1, 0.4, 0.8 wt.%) alloys were investigated systematically. For the microstructure and mechanical properties, SrZn13 phase was newly formed due to the addition of 0.1 wt.% Sr, improving the yield strength, ultimate tensile strength and elongation from (85.33±2.86) MPa, (106.00±1.41) MPa and (15.37±0.57)% for pure Zn to (107.67±2.05) MPa, (115.67±2.52) MPa and (20.80±2.19)% for Zn−0.1Sr, respectively. However, further increase of Sr content led to the deterioration of the mechanical properties due to the stress concentration and cracks initiation caused by the coarsening SrZn13 particles during tensile tests. For in vitro degradation, since micro galvanic corrosion was enhanced owing to the formation of the inhomogeneously distributed SrZn13 phase, the corrosion mode became non-uniform. Corrosion rate is gradually increased with the addition of Sr, which is increased from (11.45±2.02) μm/a (a=year) for pure Zn to (32.59±3.40) μm/a for Zn−0.8Sr. To sum up, the as-extruded Zn−0.1Sr alloy exhibited the best combination of mechanical properties and degradation behavior.