Representative microstructures of several Zn-based alloys under different processing conditions: (a) Zn-Mg, (b) Zn-Cu, (c) Zn-Mn: tensile twinning is highlighted in red, (d) Zn-Al: white and red arrows represent Zn + Mg 2 Zn 11 eutectic and b(Zn) + a(Al) monotectoid constituents, respectively, (e) Zn-Cu-Mg, (f) Zn-Li, (g) Zn-Ag. All compositions are given in wt%. Adapted with permission from [23,79,84,88,91,92]. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

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... to obtain stent-sized mini tubes. In agreement with the Zn-Mg phase diagram, the microstructures of hypoeutectic Zn-0.15Mg, Zn-0.5Mg and Zn-1Mg consisted of Zn dendritic grains embedded in a eutectic matrix of Zn and Mg 2 Zn 11 . In contrast, Zn3Mg exhibited a fully eutectic microstructure with fine alternate lamellae of Zn and Mg 2 Zn 11 (Fig. 4a). In all the alloys, increasing the Mg content decreased the grain size [79]. Jin et al. [64] reached this same conclusion from extruded and drawn Zn-Mg alloys containing 0.08, 0.005 and 0.002 (wt%) ...

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... forms a mixture of Zn and CuZn 5 phases. Zn-xCu (x = 1, 2, 3, 4 wt%) binary alloys were investigated by Tang et al. [84] and Niu et al. [85] for absorbable cardiovascular implants. The as-cast microstructures consisted of dendritic CuZn 5 phase embedded in primary Zn matrix, with an increasing dendritic volume fraction at higher Cu concentrations (Fig. 4b). Homogenization of the alloys at 360 °C did not alter the microstructure, which indicated the thermal stability of the CuZn 5 intermetallic. Further hot-extrusion processing caused grain refinement, especially in the regions closer to the CuZn 5 phase, due to dynamic recrystallization. The effect of small Mg additions to the Zn-Cu ...

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... of small Mg additions to the Zn-Cu system was investigated through a series of Zn-3Cu-xMg (x = 0, 0.1, 0.5, 1.0 wt%) ternary alloys by Tang et al. [86]. Increasing Mg concentration gradually refined the grain size and led to a more homogenous microstructure, containing both the CuZn 5 and Mg 2 Zn 11 phases, in the as-cast and asextruded alloys (Fig. 4e), which resulted in a higher tensile strength and a relatively uniform corrosion behavior. Yue et ...

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... (x = 0.2, 0.4, 0.6 wt%) were studied by Sun et al. [88]. The Zn-0.2Mn alloy showed only Zn-rich phases, whereas the MnZn 13 intermetallic was identified in the Zn-0.4Mn and Zn-0.6Mn alloys. The average grain size of the hot-extruded alloys decreased notably with the addition of 0.2 (wt%) Mn and remained relatively constant with higher Mn content (Fig. 4c). In addition, the twinning volume fraction (highlighted in red in Fig. 4c) decreased gradually with increasing Mn content, while a basal texture was maintained regardless of Mn content. Consequently, dislocation movement was enhanced with higher Mn content resulting in an increase of the e f at the expense of the tensile strength. ...

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... showed only Zn-rich phases, whereas the MnZn 13 intermetallic was identified in the Zn-0.4Mn and Zn-0.6Mn alloys. The average grain size of the hot-extruded alloys decreased notably with the addition of 0.2 (wt%) Mn and remained relatively constant with higher Mn content (Fig. 4c). In addition, the twinning volume fraction (highlighted in red in Fig. 4c) decreased gradually with increasing Mn content, while a basal texture was maintained regardless of Mn content. Consequently, dislocation movement was enhanced with higher Mn content resulting in an increase of the e f at the expense of the tensile strength. Sotoudeh Bagha et al. [89] prepared Zn-xMn (x = 4, 24 wt%) alloys via powder ...

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... The latter is not stable below 275 °C and transforms into a-Al through a monotectoid reaction. Zn-xAl (x = 0.5, 1 wt%) binary alloys were explored by Mostaed et al. [79] for absorbable stent applications. The as-cast microstructures consisted of a Zn matrix with a small content of a Zn-Al eutectoid mixture located mainly at the grain boundaries (Fig. 4d), which act as pinning points and therefore delay grain growth leading to finer grain sizes. Further solution treatment at 350 °C was found to dissolve the eutectic constituent in the Zn-rich matrix, forming a supersaturated solid solution. Despite the toxicity concern of Al, higher Al-containing alloys, such as Zn-xAl (x = 1, 3, 5 ...

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... also been alloyed with Ag, which presents a solubility limit in Zn of about 6 (wt%) at 431 °C, where a peritectic reaction transforms AgZn 3 and liquid into a Zn solid solution (Fig. 3g). Sikora-Jasinska et al. [91] observed that the as-cast microstructure of Zn-xAg (x = 2.5, 5, 7 wt%) alloys consisted of a primary Zn matrix and AgZn 3 dendrites (Fig. 4g), with an increasing volume fraction of the latter at higher Ag contents. After solution treatment at 410 °C, the AgZn 3 dendrites were fragmented into equiaxed particles uniformly dispersed through the Zn matrix. Upon 6 h and 12 h solution treatments for the 2.5-5 and 7 (wt%) Ag alloys, respectively, the AgZn 3 phase was dissolved ...

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... is another element added to Zn, and its maximum solubility in Zn is only about 0.1 wt% at 403 °C (Fig. 3h). At that temperature, a eutectic reaction transforms the liquid phase into Zn and b-LiZn 4 , which further transforms to a-LiZn 4 below 65 °C. (Fig. 4f). After hot rolling, the Zn-0.4Li and Zn-0.7Li alloys exhibited a severe rolling texture with finer dendrites and grains, while Zn-0.2Li presented equiaxed grains due to dynamic recrystallization. ...