The role of Cu addition in the metallurgical features, mechanical properties, and cytocompatibility of cardiovascular stents biodegradable Zn-based alloy

Recently, Zn-based alloys have been considered a promising biodegradable material due to their excellent physiological degradable behavior and acceptable biocompatibility. However, poor mechanical performance limits its application, especially for cardiovascular stents. In this work, novel biodegradable Zn-xCu-0.8Mn-0.4Ag (x = 1, 2, 5 %Wt) alloys were prepared. The effects of Cu addition on microstructure, mechanical properties, and cytotoxicity of alloys were investigated. To modify the microstructure and improve the properties of the alloys, the secondary process of hot extrusion was applied. The results of XRD analysis showed that the above alloys have four phases of α-Zn, CuZn5, MnZn13, and Zn3Ag. After hot extrusion, the secondary phase particles were broken and spread throughout the structure. According to the hardness test, due to the presence of CuZn5 hard secondary phase particles, the hardness increased gradually. The tensile test showed that adding copper and performing a hot extrusion process can significantly improve mechanical properties. The as-extruded alloys exhibited suitable mechanical performances mainly due to the combined effects of solid solution strengthening, and second phase precipitation hardening. In particular, yield strength, ultimate tensile strength, and elongation for Zn-xCu-0.8Mn-0.4Ag (x = 5 wt) alloy reached the value of 255.47, 359.82 MPa, and 35.84 %, respectively, which meets the requirements of cardiovascular stent well. Cytotoxicity test also showed that homogenized and as-extruded alloys have acceptable in vitro cytocompatibility. According to the obtained results, Zn-xCu-0.8Mn-0.4Ag extruded alloys can be considered as potential candidates for cardiovascular stents.