Mechanical properties, degradation action, and biocompatibility of in situ nanoparticle-reinforced MgxZny/Zn composite prepared via roll bonding.

Abstract

Zinc (Zn)-based alloys and composites are anticipated to emerge as a category of degradable metallic biomaterials with exceptional prospects for bone-implant applications owing to their superior biocompatibility and biofunctionality. Unfortunately, the limited strength of Zn alloys in their as-cast state restricts their use in clinical applications. In this study, we started with pure magnesium (Mg) powders and Zn sheets, and successfully fabricated Mg_xZn_y/Zn composites using accumulative roll bonding (ARB). The influence of varying ARB cycle numbers on their microstructures, performance in relation to mechanical parameters, corrosion resistance, and cytotoxicity was comprehensively studied. Following 15 ARB cycles, the composites demonstrated a refined Zn matrix phase with grains of 0.3 μm and uniformly distributed in situ nanoparticle reinforcements of Mg₂Zn₁₁ and MgZn₂. The composites after 15 ARB cycles exhibited an ultimate tensile strength of 560 MPa, yield strength of 540 MPa, and elongation of 12 %, significantly better than the mechanical properties of most Zn alloys reported to date. The significant improvement in the composites' strength is primarily attributable to refinement of grain size and dispersion strengthening, both of which are facilitated by the in situ incorporation of nanoparticles. The corrosion rate reduced with more ARB cycles and after 15 ARB cycles the composites had an electrochemical corrosion rate of 150.2 μm/y and an immersion degradation rate of 50.6 μm/y. Further, an extract at 12.5 % concentration had a cell viability of 92.2 % toward MG-63 cells, indicating good biocompatibility. STATEMENT OF SIGNIFICANCE: This work reports on Mg_xZn_y/Zn composites fabricated by accumulative roll bonding (ARB). The composite after 15 ARB cycles exhibited an ultimate tensile strength of 560 MPa, yield strength of 540 MPa, and elongation of 12 %, significantly higher than the mechanical properties of most Zn alloys published in the literature to date. The corrosion rate of the composites decreased with increasing number of ARB cycles and after 15 ARB cycles they showed an electrochemical corrosion rate of 150.2 μm/y and immersion degradation rate of 50.6 μm/y. Further, a 12.5 % concentration extract showed a cell viability of 92.2 % in relation to MG-63 cells, indicating good biocompatibility.