Revealing the mechanical and degradation properties of the Zn-Cu-Ti alloy with ununiform heterostructure

Abstract

Zn alloy has attracted much attention in recent years as a new biomedical degradable material. However, how to simultaneously achieve its high strength and high ductility is a bottleneck problem to be solved. In this study, the Zn-2.0Cu-0.1Ti alloy with ununiform heterostructure, consisting of the barren areas without CuZn5 phase and the regions enriched with CuZn5 phase, was designed and successfully fabricated through controlled stir casting and hot extrusion. Uniaxial tensile test and Vickers hardness test were applied to reveal the mechanical properties of the Zn-2.0Cu-0.1Ti alloy, while electrochemical test and immersion test were used to characterize its degradation properties. The novel heterostructure was systematically examined by optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). It was found that the yield strength and ultimate tensile strength of the present Zn-2.0Cu-0.1Ti alloy reach 241.2 ± 4.7 MPa and 265.8 ± 1.3 MPa, showing 294.4% and 230.3% improvement over those of pure Zn. Even more surprising is that the improved strength can be achieved without sacrificing ductility. The substantially increased strength can be mainly attributed to the strengthening mechanisms of grain refinement and Orowan looping, and the maintenance of good ductility thanks to the excellent dislocation storage ability of the present heterostructure. At the same time, the corrosion rate of the alloy in simulated body fluids also reaches the industry standard for orthopedic implants. This study not only sheds light on the design and fabrication of Zn-based material for surgical implantation application but also provides a feasible route to improve the mechanical properties of other precipitates reinforced alloys.