Impact of microalloying element Ga on the glass-forming ability (GFA), mechanical properties and corrosion behavior of Mg–Zn–Ca bulk metallic glass

By virtue of its high corrosion resistance and desirable mechanical properties, Mg-based bulk metallic glass (BMG) is a promising candidate material for the biodegradable implants. To investigate the impact of microalloying element Ga on the glass-forming ability (GFA) and its effect on the mechanical properties and corrosion behaviors of Mg–Zn–Ca BMG, a series alloys of (Mg66Zn30Ca4)100-xGax (x = 0, 0.25, 0.5, 0.75, 1.0 and 1.25) were synthesized and investigated in this study. According to the XRD results and SEM (backscattered electron) images, the critical diameter (Dc) of Mg66Zn30Ca4 BMG is about 3.5 mm, and 1.0 at.% Ga addition improves the Dc to about 5 mm. Meanwhile, the 1.0 at.% Ga addition improves the fracture strength of Mg–Zn–Ca BMG from 651 MPa to 752 MPa. The corrosion behavior and mechanism of different metallic glass samples were investigated. According to the results of electrochemical tests and immersion test, the addition of Ga can help to form the passive film on the metallic glass substrate and improve its corrosion resistance. Besides, the relationship between the alloy composition and glass-forming ability (GFA) was postulated and interpreted by the theory of binary alloy phase diagrams.