Microstructure and mechanical properties of a phase-separating Mg-based bulk metallic glass

• A phase-separated (Mg0.585Cu0.305Y0.11)97(Zr0.35Ti0.3Be0.275Cu0.075)3 was found in this paper.
• A fully amorphous structure containing two different glassy phases caused by phase separation was observed.
• The improvement of the mechanical properties of the BMG is attributed to the shear-band multiplication and interaction caused by the harder Zr-rich amorphous spherical particle.

Samples of the (Mg0.585Cu0.305Y0.11)97(Zr0.35Ti0.3Be0.275Cu0.075)3 bulk metallic glass (BMG) with 3 mm in diameter were successfully fabricated by copper mould casting method. The amorphous nature, thermal stability, microstructure and mechanical properties of the alloy were investigated by using X-ray diffraction (XRD), differential scanning calorimeter (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electronic testing machine. The results show that the alloy presents a fully amorphous structure containing two glassy phases caused by phase separation. The Zr-rich amorphous spherical phase is distributed in the Mg-rich glassy matrix of the as-cast sample. Under uniaxial compressive loading, the compressive fracture strength, elastic strain and plastic strain of the BMG with a diameter of 3 mm are 1026 MPa, 2.2% and 0.3%, respectively. The ridge form vein-like patterns and multiple shear bands are observed in the fracture surface, indicating the improvement of the mechanical properties of the alloy. The formation of phase separation and the corresponding fracture mechanism were discussed.