Developing high elongation of Ca-containing Zn alloys with superior osteogenic and antibacterial properties

The development of high-strength zinc (Zn) alloys significantly contributes to the field of orthopedics by enhancing their osteogenic properties. Calcium (Ca) is pivotal for bone composition; however, its incorporation into the Zn matrix often hampers elongation due to the formation of large-sized CaZn 13 phases. In this study, two Zn alloys with different Ca contents were prepared, and their microstructures, mechanical properties, corrosion behavior and biocompatibility were investigated. Results indicate that the Zn alloy with high Ca content exhibits large-sized and high-volume-fraction CaZn 13 phases, which do not significantly change during equal channel angular pressing (ECAP). The grain sizes of ECAPed Zn alloys decreased from 36.75 μm and 35.81 μm of as-cast state to 4.32 μm and 1.71 μm, respectively. Refined microstructures contributed to the improvement of mechanical properties of Zn alloys, which have elongation over 15% higher than that of all Zn-Mg-Ca alloys reported so far. The high elongation of Zn alloys originates from the inhibition of the propagation of microcracks which generated from the Zn/CaZn 13 interphase. Moreover, the formation of large-sized CaZn 13 phases leads to the severe local corrosion through enhancing galvanic effect, finally increasing corrosion rate. During degradation, the release of metallic ions, such as Zn 2+ , Mg 2+ , and Ca 2+ , are beneficial to the cell viability and osteogenic properties. And the accelerated release of Zn 2+ plays a role in antibacterial performance. These results are very helpful for promoting the application of biodegradable Zn alloys in the field of orthopedics. • A novel Zn-Mg-Mn-Ca alloy containing CaZn 13 phases has fracture elongations of 18.4%, which is higher than that of reported Zn-Mg-Ca alloys. • After ECAP, the average grain size of Zn alloys decreased as Ca increased, which is attributed to DRX refinement and the restricted growth by CaZn 13 phase. • The Zn alloys alloys exhibited the controllable corrosion rate by altering Ca content. • The two Zn-Mg-Mn-Ca alloys have superior cell compatibility, osteogenic properties, as well as anti-bacterial properties.