Creep behavior and mechanisms of biodegradable Zn-0.4Li-0.45Mn alloy under physiological and sterilization temperatures at various stress levels

The creep behavior of Zn-0.4Li-0.45Mn alloy, prepared by melt casting and hot extrusion as a potential biodegradable implant material, was investigated under stresses ranging from 70 to 260 MPa. Creep tests were conducted at 37°C, 51°C, and 121°C, corresponding to body temperature, ethylene oxide sterilization, and autoclaving sterilization temperatures, respectively. The study found that the alloy exhibited significant creep deformation over 750 hours, particularly under low-stress conditions at 37°C, where it demonstrated a high true stress exponent (3.70). The alloy's creep characteristics showed clear temperature dependence within this stress range, with an apparent creep activation energy of 74.5 kJ/mol at 70 MPa, suggesting that the creep mechanism is primarily controlled by a stress-sensitive, thermally activated process. Microstructural analysis revealed significant grain deformation on the alloy surface before and after creep, and scanning electron microscopy images showed grain boundary sliding, indicating this process as the primary mechanism for creep failure. Additionally, the Maxwell viscoelastic model was used to accurately characterize the alloy's behavior during the steady-state creep phase, with model fitting showing strong agreement with experimental data. These results not only enhance the understanding of the creep behavior of zinc alloys in biomedical applications but also provide a scientific basis for their potential use in materials science and engineering.