Effects of a high-voltage pulsed magnetic field on the solidification structures of biodegradable Zn-Ag alloys

Abstract The physical and chemical properties of biodegradable zinc alloys are closely related to their microstructures. Therefore, various techniques are being attempted to change their microstructures. However, little work has been done to control the initial solidification structures of the biodegradable zinc alloys, which play an important role in determining their final properties. In view of this, Zn-Ag alloys with different compositions were solidified under a high-voltage pulsed magnetic field (HVPMF) in this work. The results show that the primary η-Zn grains in the isomorphous Zn-2.5 wt% Ag alloy are transformed from coarse dendrites to fine globular grains with increasing the HVPMFs. Also, its macrostructural homogeneity in the specimens is enhanced gradually. Moreover, the primary e-AgZn3 dendrites in the hypoperitectic Zn-4.0 wt% Ag and hyperperitectic Zn-9.0 wt% Ag alloys are refined and “levitated” by the HVPMFs. Correspondingly, the peritectic η-Zn grains that nucleate on the fine primary e-AgZn3 particles are also significantly refined. In addition, when applying the HVPMFs in separate solidification stages of these two alloys, it is found that the HVPMFs mainly have a crucial effect on the structures in the early stage. The modification of the solidification structures in the Zn-Ag alloys is attributed to the forced convection and the Joule heat induced in the liquid-solid two-phase zone by the HVPMFs.