Phase separation and plastic deformation in an Mg-based bulk metallic glass

Abstract

The glass formation, microstructure and thermal stability of Mg 60Cu 10Ni 16Nd 14 bulk metallic glass (BMG) were investigated by using copper mould casting, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and differential scanning calorimetry. The results show that at least 3 mm in diameter of BMG with a larger supercooled liquid region up to 61 K was obtained for the designed composition. Phase-separated regions with diameter size <2 μm are homogeneously distributed in the as-cast sample. Under uniaxial compressive loading, the designed Mg-based BMG demonstrates a remarkable macroscopic plastic strain of 2.5% and no work hardening behavior for the sample of 3 mm in diameter at room temperature. The improvement of mechanical properties was explained by the extensive shear band formation, interaction, and multiplication due to the heterogeneous microstructure caused by the phase separation during solidification. The low yielding behavior for the BMG was suggested to come from the random formation of shear bands before reached the plateau stress.