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A common problem for Zn alloys is the trade-off between antibacterial ability and biocompatibility. This paper proposes a strategy to solve this problem by increasing release ratio of Ca2+ ions, which is realized by significant refinement of CaZn13 particles through bottom circulating water-cooled casting (BCWC) and rolling. Compared with conventionally fabricated Zn-0.3Ca alloy, the BCWC-rolled alloy shows higher antibacterial abilities against E. coli and S. aureus, meanwhile much less toxicity to MC3T3-E1 cells. Additionally, plasticity, degradation uniformity, and ability to induce osteogenic differentiation in vitro of the alloy are improved. The elongation up to 49 %, which is the highest among Zn alloys with Ca, and is achieved since the sizes of CaZn13 particles and Zn grains are small and close. As a result, the long-standing problem of low formability of Zn alloys containing Ca has also been solved due to the elimination of large CaZn13 particles. The BCWC-rolled alloy is a promising candidate of making GBR membrane.

Effects of Fe addition on mechanical properties and microstructures of biodegradable Zn-Mn alloys are unknown yet, which will be revealed in the present study. Minor addition of Fe results in formation of (Fe, Mn)Zn13 phase, which can have a (Fe, Mn)Zn13/MnZn13 core/shell structure. The core and the shell exhibit a coherent orientation relationship (OR). Between them, there exists a thin interlayer with an irrational OR with respect to either the core or the shell. Although the as-cast alloys are very brittle, their ductilities and strengths can be significantly improved through hot rolling, owing to significant grain refinement of Zn matrix and refinement of the second phase particles. Elongation of the hot-rolled Zn-1Mn-0.1Fe alloy is about 4.8 times of that of the hot-rolled Zn-1Mn-0.5Fe alloy, indicating that ductility of Zn-Mn-Fe alloy is very sensitive to Fe content. Keywords: Alloy design, Thermomechanical processing, Microstructure, Transmission electron microscopy, (Fe, Mn)Zn13