Effect of Fe Addition on the Microstructure, Corrosion Behavior, and Mechanical Properties of Zn-3.5Al-1.5Cu Alloy for Biomedical Application

Zn-3.5Al-1.5Cu-xFe (x = 0,0.1,0.3) alloys were prepared by metal mold casting. The effect of Fe addition on the microstructure, corrosion behavior in 3.5 wt.% NaCl solution and simulated body fluid, and mechanical properties of Zn-3.5Al-1.5Cu alloys were systematically investigated. The results revealed that the microstructures predominantly consisted of the η phase (Zn solid solution) and α (Al) + η eutectic. Fe addition refined the grain size of η phase, reduced its volume fraction, and led to the formation of (Fe, Al) Zn₁₃ intermetallic compounds. The microhardness increased with Fe content. The tensile strength rose from 269 MPa (0.1 wt.% Fe) to 284 MPa (0.3 wt.% Fe). The Zn-3.5Al-1.5Cu-0.1Fe alloy exhibited the highest elongation (2.8%), representing a 55.56% improvement over the Fe-free alloy. Fracture analysis indicated predominantly cleavage fracture. Electrochemical testing and immersion testing demonstrated that Fe addition reduced the corrosion rate. Specifically, the alloy adding 0.1 wt.% Fe exhibited the lowest self-corrosion current density (5.855 μA cm⁻²) and corrosion rate (74 ± 3 μm year⁻¹) in electrochemical test.