Effect of double continuous extrusion on microstructure, mechanical properties, and corrosion behavior of Mg-2Zn-1Gd alloy for biodegradable implants

Magnesium alloys offer enormous potential as biodegradable implant materials due to their biocompatibility, low density, and bone-like mechanical qualities, making them ideal for orthopedic and cardiovascular implants. However, rapid depreciation in physiological circumstances results in initial mechanical breakdown and hydrogen gas release, which can cause tissue damage. Alloying, thermomechanical processing, and surface treatments are all necessary methods for controlling the degradation rate while retaining implant stability. This study evaluates the effects of double continuous extrusion (DCE) and Gd addition on the microstructural evolution and mechanical and corrosion behavior of the Mg-2Zn alloy. The Mg3Zn3Gd2 secondary phase is produced when Gd and DCE are combined, as shown by XRD and microscopy. Refined microstructures less than 2 µm are produced as a result of improving corrosion behavior and mechanical characteristics. The DCE sample of Mg-2Zn-1Gd has yield stress (YS), ultimate tensile strength (UTS), and elongation values of 350 MPa, 425 MPa, and 20 %, respectively, due to refined grain and secondary phase dispersion, which are above the minimal requirement for biodegradable implants. Precipitation strengthening and Hall-Petch strengthening are responsible for the hardness enhancement with DCE. However, because of the coupling between the Mg matrix and the Mg3Zn3Gd2 particles, galvanic corrosion accelerates. Interestingly, DCE reduces galvanic effects and improves surface protection, resulting in a lower corrosion rate compared to as-cast Mg-2Zn and Mg-2Zn-1Gd and extruded samples. All of them suggest that double continuously extruded Mg-2Zn-1Gd alloy has a bright future in biodegradable applications, particularly in orthopedic implants.