Determining the microstructure of zinc-lithium alloys for enhanced biomedical devices

Gatan instrument used

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Background

Metallic zinc has many interesting properties for biomaterial applications, such as intravascular stents, due to its excellent formability and biocompatibility while biodegrading at a rate commensurate with the body’s ability to heal. However, the mechanical properties of pure zinc offer insufficient strength for critical applications such as biodegradable intravascular stents. Consequently, improving the mechanical properties of zinc alloys remains an urgent task.

Alloying zinc with lithium is of great interest due to the possibility of work hardening alloys formed with a Zn-LiZn₄ eutectic microstructure. However, αLiZn alloys share a common hexagonal close-packed (HCP) crystal structure with many stable Li_xZn_y phases possible including αLiZn₄, αLi₂Zn₅, αLiZn₂, αLi₂Zn₃, and αLiZn; these phases consist of just 2.6, 4.1, 5.0, 6.6, and 9.6 wt.% lithium respectively. However, the inability to differentiate these phases using conventional analysis techniques such as energy dispersive x-ray spectroscopy (EDS) or image quality or grain size data derived from electron backscatter diffraction (EBSD) maps presents a significant challenge in describing the microstructure, therefore impeding the understanding of hardening mechanisms in ZnLi alloys and preventing their adoption as biomedical devices.