Quaternary Mg–Zn–Y–Gd Alloys: Controlled biodegradation via Gd Alloying and thermomechanical treatment

Magnesium alloys show promise as biodegradable implants but require degradation rate control. This study examines Gd additions (0–2 wt.%) and thermomechanical processing (hot rolling, extrusion) on Mg-2Zn-0.5Y alloys. XRD and microscopy reveal Gd forms Mg₃ Zn₃ Gd₂ phases, refining grains to ∼205 μm without altering the α-Mg matrix. Hardness increases with Gd content due to precipitation and Hall-Petch strengthening from dynamic recrystallization. However, Gd elevates galvanic corrosion between Mg₃ Zn₃ Gd₂ and the matrix, raising corrosion rates by ∼48% at 2 wt.% Gd. Extrusion mitigates galvanic effects, reducing corrosion versus as-cast alloys. These insights on synergies between composition, microstructure, and thermomechanical processing advance knowledge for designing biodegradable Mg implants with tailored degradation.