Tailoring microstructure, mechanical properties, and degradation of biodegradable Mg-Zn-Gd alloys: Effects of Er addition and thermo-mechanical treatment

Magnesium alloys emerge as biodegradable implant materials due to their susceptibility to corrosion in physiological environments. In this study, Mg-2Zn-1Gd and Mg–2Zn-1Gd-1Er alloys were developed as potential biodegradable biomaterials. The alloys were fabricated by metal mold casting, heat-treated at 400°C for 24 h to homogenize the microstructure, and subsequently thermo-mechanically processed by hot rolling and hot extrusion. X-ray diffraction analysis indicated an α-Mg matrix with a secondary phase consistent with Mg 3 Zn 3 Gd 2 (W-phase). Microscopy and SEM-EDS analyses of rolled and extruded alloys further identified secondary particles with compositions consistent with the Mg 3 Zn 6 Gd (I-phase) and Mg 2 Zn 3 phases. The quantity of secondary phase constituents increased with the addition of Er. Hardness testing showed improvements in hardness with Er alloying and rolling. The results of in vitro degradation experiments, including electrochemical measurements and weight-loss tests, revealed that Gd and Er could elevate the corrosion potential of Mg in phosphate-buffered saline (PBS) and reduce the degradation rate. The results indicate the promising potential of Mg-Zn-Gd-Er alloys as biodegradable implants, with tailored degradability achieved through compositional design and thermomechanical processing.