A Comparative Study of As-Cast Alloys of ZW21 with Varied Element Additions, Investigating Dry and Corrosive Wear in Body Fluid

Magnesium (Mg) alloys have emerged as a promising candidate for orthopedic implants due to their exceptional biocompatibility, biodegradability, and bone-like properties. However, their rapid corrosion in physiological environments and wear under mechanical stresses remain critical challenges. Wear resistance testing is essential for orthopedic implants to ensure longevity and prevent adverse biological responses, such as the release of metal ions or debris, which can cause inflammation or implant failure. To overcome these limitations, the incorporation of alloying elements in Mg is believed to be a method that promotes higher mechanical strength and improves corrosion resistance. This study investigates the microstructure and mechanical properties—especially the wear behavior and friction characteristics—of Mg-2Zn-1Y (ZW21) as-cast alloys enhanced with various alloying elements (Nd, Ce, Zr, La, Gd, Ag, Ca). Fabricated using the die-casting method, these alloys were subjected to both dry and corrosive wear tests to comprehensively evaluate their tribological performance. Dry wear tests served as a baseline to assess the intrinsic mechanical properties and establish a reference for corrosive behavior, while wear tests conducted in Hank’s solution simulated physiological conditions to elucidate the combined effects of wear and corrosion. XRD analysis revealed the presence of diverse crystalline phases in the alloys, including the α-Mg matrix, I-phase (Mg₃Zn₆Y₂), W-phase (Mg₃Zn₃Y₂), LPSO-phase (Mg₁₂ZnY), and secondary phases, such as Mg₄₁Nd₅, Mg₁₂Ce, and Mg4Ag, highlighting the influence of alloying elements and Zn/Y ratios on phase formation. The addition of alloying elements—particularly Zr, Nd, and Ce—to the Mg-2Zn-1Y alloy refined grain sizes (from 84 μm to 46 μm) and enhanced hardness (from 51.2 HV to 68.8 HV) by promoting intermetallic phase formation, grain refinement, and solid-solution strengthening. Alloying elements in Mg-2Zn-1Y alloys significantly affected wear behavior and friction coefficients. Higher Nd content enhanced dry wear resistance due to the formation of Mg₄₁Nd₅, while higher Ce content improved corrosive wear resistance due to protective intermetallics. Friction coefficients were lower in Hank’s solution due to its lubricating effect, though micro-galvanic effects around phases like Ca₂Mg₆Zn₃ increased corrosion rates in specific alloys.