Synchronous enhancement of corrosion resistance and mechanical properties of Mg-Zn-Ca alloys by grain refinement using equal channel angular pressing

To investigate the effect of microstructure evolution on corrosion behavior and strengthening mechanism of Mg-1Zn-1Ca (wt.%) alloys, as-cast Mg-1Zn-1Ca alloys were performed by equal channel angular pressing (ECAP) with 1 and 4 passes. The corrosion behavior and mechanical properties of alloys were investigated by optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), electrochemical tests, immersion tests and tensile tests. The results showed that mechanical properties improved after ECAP 1 pass; however, the corrosion resistance deteriorated due to high-density dislocations and fragmented secondary phases by ECAP. In contrast, synchronous improvement in the mechanical properties and corrosion resistance was achieved though grain refinement after ECAP 4 passes; fine grains led to a significant improvement in the yield strength, ultimate tensile strength, elongation, and corrosion rate of 103 MPa, 223 MPa, 30.5%, and 1.5843 mm/a, respectively. The enhanced corrosion resistance was attributed to the formation of dense corrosion product films by finer grains and the barrier effect by high-density grain boundaries. These results indicated that Mg-1Zn-1Ca alloy has a promising potential for application in biomedical materials.