Improving the mechanical properties and corrosion resistance of Mg-2Zn-0.5Zr-1.5Dy alloy by combining hot extrusion with subsequent fluorinated coating

A novel Mg-2.0Zn-0.5Zr-1.5Dy (wt.%) alloy used for orthopedic applications was prepared by hot extrusion deformation, followed by fluorinated coating treatment. The corrosion behavior, film formation mechanism, and corrosion resistance of as-cast, extruded (E460), and coated (CE460) specimens were investigated. Results demonstrated that the grain size after extruding was refined significantly, and the mechanical properties improved greatly while the corrosion resistance decreased slightly. The average corrosion rate of extruded sample E460 immersed in simulated body fluid (SBF) for 240 hours was about 1.030 f 0.017 mm y-1, and the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) were 310 f 17 MPa, 321 f 25 MPa, 11.1 f 1.9 %, respectively. CE460 specimen was treated by combining hot extrusion with subsequent fluorinated coating; the mechanical properties changed less, whereas the corrosion resistance increased dramatically, and its average corrosion rate decreased from 1.03 f 0.017 to 0.070 f 0.004 mm y-1. The comprehensive performance was improved greatly by combining hot extrusion with subsequent fluorinated coating. The corrosion mechanism for specimens under extruded and annealed conditions was analyzed.