Effects of Sr on Microstructure and Properties of Zn-Sn-based Degradable Biomedical Alloys

Abstract:

The microstructure, mechanical properties, corrosion behavior, and cytotoxicity of biodegradable Zn-1.5Sn-xSr alloys (x=0, 0.3, 0.5, wt%) were investigated. The results indicate that the addition of Sr introduces minor SrZn₁₃ phases, enhancing the yield strength and elastic modulus of the Zn-1.5Sn-xSr alloys. Transmission electron microscopy analysis reveals the existence of the SrZn₁₃ phase through the calibration of diffraction spots. Electrochemical tests confirm the formation of a passive film on Zn-1.5Sn-xSr alloys, with Zn-1.5Sn-0.3Sr alloy exhibiting higher corrosion resistance. Further immersion tests and X-ray photoelectron spectroscopy analysis elucidate the elemental composition and content of the passive film formed by the corrosion products, which primarily consists of oxides, hydroxides, and slightly soluble carbonates and phosphates. In terms of cytotoxicity, the Zn-1.5Sn-xSr alloys exhibit excellent biocompatibility. MTT experiments show that the cell viability can reach up to 130%, which is attributed to the release of Sr²⁺ during the degradation. Sr²⁺ and Zn²⁺ ions jointly promote the cell proliferation and differentiation.