Microstructure evolution and mechanical properties of bulk nanocrystalline Zn−Cu−Sr−Li alloy processed by high-speed rolling
Bulk nanocrystalline Zn−3Cu−0.2Sr−xLi (x = 0, 0.2, 0.4 wt.%) alloys were fabricated via high-speed rolling (HSR) to address the insufficient mechanical performance of as-cast Zn alloys for biodegradable bone fixation. The HSR process introduced dense dislocations that supplied driving force for recrystallization. Li addition promoted the formation of ε and β phases, which provided abundant heterogeneous nucleation sites and a strong Zener pinning effect, facilitating recrystallized grain nucleation while restricting growth. The average grain size of the 0.4Li alloy was refined from 181.8 μm in the as-cast state to 50 nm after rolling. The rolled 0.4Li alloy achieved an ultimate tensile strength of 433.3 MPa, a yield strength of 382.2 MPa, and an elongation of 15.2%. Relative to the as-cast Li-free alloy, the rolled 0.4Li alloy exhibited a 173% increase in yield strength and a 591% improvement in elongation. Nanocrystalline strengthening was the dominant mechanism, contributing 70.4% to the total yield strength. The fracture mode of the 0.4Li alloy transitioned from brittle fracture in the as-cast condition to ductile fracture after rolling. The combination of alloying design and HSR offers a viable route to bulk nanocrystalline Zn alloys with superior mechanical performance for temporary bone fixation applications.