Flow stress stabilization of Zn-Cu-Mn-Mg alloys using thermomechanical processing

Zinc-based alloys are potential candidates for bioabsorbable metallic devices due to their application-appropriate corrosion rates and biocompatibility. However, strain softening and rate sensitivity in tensile testing remain as challenges for their use in load bearing applications. In this study, three different Zn-xCu-yMn-0.05Mg (x = 0.5, 1.0 wt%, y = 0.4, 0.6 wt%) alloys were formulated and their microstructure and tensile properties in the room-temperature rolled condition were characterized. Additionally, the effect of short-time annealing at 320 °C on the strain softening and strain rate sensitivity of alloys was studied. The results indicate that dissolution of secondary phases and grain coarsening lead to the suppression of strain softening and strain rate sensitivity. The evolution of microstructure during the room-temperature tensile testing indicates that dynamic recrystallization is responsible for strain softening and can be eliminated by tuning the fraction of secondary phases and underlying grain size. The formulated alloys are not susceptible to natural aging and show good thermal stability during aging up to 200 °C for 60 h due to the pinning effect of MnZn₁₃ precipitates on the grain boundaries.