Zn-Li-based
alloys have drawn great attention as promising candidates for load-bearing sites, such as intramedullary nails and
bone plates. They possess high monotonic strength (over 500MPa) and better pitting resistance with
lithium-rich layers acting as barriers for corrosion attack under (quasi-)static conditions. However, their response to dynamic loadings such as
fatigue is still unknown. Herein, the corrosion
fatigue behavior of a series of Zn-Li binary
alloys with different
lithium addition amounts was tested in simulated body fluid. Tensile and
fatigue strength of the materials were proportional to
lithium content while corrosion
fatigue strength was not. Extremely long cracks that extended parallel to the loading direction were found in Zn-1.0wt.%Li
alloys. These cracks propagated by selective dissolution of the
lithium-rich phase in the eutectoid regions and drastically reduced the corrosion
fatigue strength of Zn-1.0wt.%Li
alloy owing to exacerbated crack propagation. To sum up, Zn-Li binary
alloys showed
fatigue strength comparable to pure
iron and pure
titanium, which confirmed their loading capacity under dynamic conditions. STATEMENT OF SIGNIFICANCE: Zn-Li-based
alloys are qualified as biodegradable metals and are dedicated to load-bearing applications. Current research has shown that
lithium can suppress pitting corrosion by the formation of
lithium-rich layers on the
alloy surface during (quasi-)static conditions. However, how these materials respond to dynamic loading is still unknown. The present study investigated the influence of
lithium amount (0.1∼1.0wt.%) on the corrosion
fatigue behavior of binary Zn-Li
alloys. The results showed that
lithium effectively improved the mechanical strength but can harm corrosion
fatigue strength at high content due to selective dissolution of
lithium-rich phase. This demonstrated that the amount of
lithium should be controlled for optimal properties. Zn-0.8wt.%Li
alloy demonstrated a good combination of tensile and corrosion
fatigue strength, which can be further improved by proper alloying and thermomechanical treatment.