Impact of scandium on the microstructure, mechanical properties, corrosion behaviors and in-vitro biocompatibility of a Zn-0.1Li alloy

Abstract

The poor mechanical properties of pure zinc (Zn) restrain its applications in orthopedics, which requires high loading capacity. Alloying with lithium (Li) element can enhance strength, however, the work-hardening rate is impaired with increased Li content. Here, introducing scandium (Sc) into a low Li-containing Zn-0.1Li alloy could effectively refine its microstructure, reducing the average grain size from 10 to 4 μm. The refinement in microstructure led to a significant improvement in tensile strength, improving from 257 MPa of Zn-0.1Li to 341 MPa of Zn-0.1Li-0.1Sc, meanwhile, the work-hardening rate remained positive during the whole plastic deformation stage. The addition of Sc-impaired elongation is due to numerous microcracks formed at the Zn/ScZn₁₂ interfaces, as well as in the large-sized ScZn₁₂ particles. Corrosion tests revealed an accelerated corrosion rate due to the galvanic effect between the Zn matrix and ScZn₁₂ phase. Even so, the Zn-0.1Li-1.0Sc alloy still exhibited superior biocompatibility with rat/mouse mesenchymal stem cells and close osteogenesis capacity to the original Zn-0.1Li alloy. These findings demonstrated that the addition of Sc in low Li-containing alloys could improve mechanical strength without sacrificing the work-hardening rate and biocompatibility.