Effect of Equal Channel Angular Pressing on Properties Evaluation of Biodegradable Mg-Zn-Mn Alloy

Equal channel angular pressing (ECAP) was used to process Mg-4Zn-1Mn alloy at 300 °C using route B_c up to 4 pass with a cumulative strain of 3.2. Optical microscope (OM), microstructures results shows homogenized sample grain size was 260 µm, after 4 pass ECAP grain size was decreased to 6 µm. Electron back-scattered diffraction (EBSD) shows the misorientation angle converted from low-angle grain boundaries (LAGB) to high-angle grain boundaries (HAGB). Dislocation density and fine grains were observed from transmission electron microscope (TEM) images. Strength has been increased from 156 to 218 MPa and hardness increased to 68 Hv after 4 pass of ECAP. Fractography analysis revealed that dimple size decreases as ECAP passes increased. XRD analysis shows the peak broadening and intensity variation, because of grain refinement. The corrosion behavior of the homogenized and ECAP-processed samples were investigated by electrochemical tests using simulated body fluids (SBF) at 37 ± 1 °C. The lower corrosion resistance of ECAP-processed Mg-4Zn-1Mn alloy attributed to the strain-induced crystalline defects, subgrain boundaries and high-density dislocations. Enhanced strength and ductility combined with lower corrosion resistance of ECAP-processed Mg-4Zn-1Mn has greater potentials for biomedical implants.