Mg‒Zn‒Ca metallic glasses are regarded as promising biodegradable materials. Previous studies on this alloy system have mostly focused on the composition regions with a large critical size (D_c) for the formation of metallic glasses, while this paper investigates the composition regions with a small D_c, which has been overlooked by researchers for a long time. The effects of the addition of Ag, Nd, and Yb elements on the microstructure and mechanical properties of Mg‒Zn‒Ca metallic glasses were studied. It was found that the Mg‒Zn‒Ca metallic glass exhibits a single and uniform amorphous structure with a compressive strength of 590 MPa. After the addition of a small amount of Ag into the alloy, the amorphous matrix is retained and new precipitate phases that lead to the decrease of the compressive strength are formed. The addition of the rare earth elements Nd and Yb changes the microstructure from a single amorphous matrix to a large number of quasicrystal phases, which results in an increase in compressive strength. The compressive strength of the Mg‒Zn‒Ca‒Yb alloy increases to 606.2 MPa due to the formation of multi-layered swirling solidified structure and a large number of small quasicrystals with high microhardness. Moreover, this study can be considered as a useful supplement to the existing studies on the Mg‒Zn‒Ca alloy system; it also provides new ideas for designing the microstructure and spatial structure of quasicrystal containing alloys with high performances.

The mechanical properties and degradation behavior of both as-cast and extruded Mg_(100−7x)Zn_6xY_x alloys (x = 0.2, 0.4, 0.6, 0.8 at %) were systematically studied in this paper. The results indicated that with the increase in x value, the mechanical properties and corrosion resistance of the Mg_(100−7x)Zn_6xY_x alloys were improved. The extruded Mg_95.8Zn_3.6Y_0.6 alloy exhibited excellent mechanical properties, showing a tensile strength of 320 MPa, yield strength of 240 MPa, and elongation of 16%, which is much higher than that of commercially extruded AZ31 alloy. The weight loss experiment presented a higher degradation rate for the extruded Mg_95.8Zn_3.6Y_0.6 alloy compared with the wrought AZ31 alloy, indicating a good bioactivity and biocompatibility. More detailed and long-term studies for evaluating and further controlling the degradation behavior of Mg–Zn–Y-based alloys remain to be performed.

Mg-Zn-Ca amorphous alloys are considered as potential bone implants. A large number of works have focused on the alloys under free corrosion environment. However, the real service environment of bone implants is a kind of chemistry-mechanics interactive environment in which the materials not only suffer corrosion by body fluids but also bear applied force induced by body movement. In order to imitate the real service environment, surface morphologies and mechanical properties of Mg-Zn-Ca amorphous alloys were studied under different chemistry-mechanics interactive environments in this paper. It was found that cracks and Ca/Mg phosphates formed on the surface of amorphous alloys. The compressive strength of the alloys decreased seriously but could still reach an acceptable value to avoid material failure. Fan-shaped patterns found on all the samples implied that brittle fracture was the main fracture form. Moreover, vein-like patterns could still be found in some areas, showing a locally plastic deformation. This was the reason why the alloy could maintain a high compressive strength after severe and interactive treatments. The study could guide related works in the establishment of experimental environments in the future, which will facilitate a more accurate biomedical evaluation of bone implants.