Biodegradable magnesium (Mg) alloys are attractive for temporary implants, minimizing stress shielding, avoiding removal surgery, and supporting bone healing. This study examines the influence of neodymium (Nd) and thermo-mechanical treatments on Mg-Zn-Er alloys. Two alloys, Mg-2Zn-2Er (C1) and Mg-2Zn-2Er-2.5Nd (C2), were cast, homogenized, rolled, and extruded. Nd promoted grain refinement and stable intermetallics, as confirmed by microstructural analysis and XRD. Vickers hardness measurements showed that C2 exhibited higher hardness than C1 in all processing conditions, and that rolling and extrusion increased hardness relative to the as-cast and heat-treated states, with extruded C2 displaying the maximum hardness of 72.90 HV. Corrosion tests in phosphate-buffered saline (PBS) revealed faster degradation of C2 due to micro-galvanic effects associated with Nd-containing intermetallics, whereas rolled C1 exhibited the lowest average corrosion rate (0.385 mm/year over 240 h) among all conditions, compared with values of 11.10 and 8.78 mm/year for extruded C1 and as-cast C2, respectively. Across both alloys, rolled specimens showed lower degradation rates than their as-cast and extruded counterparts. Overall, the rolled Mg-2Zn-2Er alloy offers a favorable combination of low corrosion rate and enhanced surface hardness for further evaluation as a biodegradable implant material.
Amin et al. (Sun,) studied this question.