Enhancement of mechanical, corrosion, and biocompatibility properties of zinc alloys through magnesium and neodymium alloying for bone implant applications

Abstract

Zinc (Zn) alloys, though beneficial for biodegradable applications due to their controlled degradation, biocompatibility, and potential to aid in bone healing, often suffer from inadequate mechanical properties. To enhance their performance, this study investigates the incorporation of magnesium (Mg) and neodymium (Nd) as alloying elements and applies hot extrusion to produce Zn-based alloys with superior mechanical and biological characteristics suitable for moderate load-bearing orthopedic uses. The resulting Zn-0.1Mg-1Nd alloy exhibits a fine-grained structure with an average grain size of 1.36 µm, which enhances its tensile strength from 71 MPa for pure Zn to 381 MPa for the alloy, alongside a notable increase in elongation from 10.7% to 17.7%. These improvements fulfill the mechanical requirements for biodegradable bone-fixation devices. Corrosion tests, including electrochemical and immersion assessments in simulated body fluid (SBF), demonstrate the alloy's enhanced degradation resistance, with the lowest corrosion rate recorded at 0.094 mm year⁻¹. Additionally, the Zn-Mg-Nd alloys show good biocompatibility, as evidenced by their favorable interactions with human bone marrow-derived mesenchymal stem cells (hBMSCs) and murine macrophages (RAW 264.7), and further promote osteogenic differentiation in hBMSCs. Overall, the Zn-Mg-Nd alloy system emerges as a promising candidate for biodegradable orthopedic applications.