The effect of high temperature plastic deformation on the thermal stability and microstructure of Zr₅₅Cu₃₀Ni₅Al₁₀bulk metallic glass

The plastic deformation of Zr55Cu30Al10Ni5(numbers indicate at.%) bulk metallic glass (BMG) was conducted in the supercooled liquid region under uniaxial tension with various strain rates ranging from 8.3 × 10-4to 2 × 10-2s-1. It was found that the deformation behavior of the BMG is strongly dependent on strain rate. Thermal and structural investigations revealed that the plastic deformation reduced the thermal stability of Zr55Cu30Al10Ni5BMG and promoted crystallization or reordering of the amorphous structure. To clarify the correlation between strain and structure of the BMG, the sample that was deformed at a high strain rate and exhibited significant necking was selected for a detailed investigation of its structure in different parts (e.g., the tip, middle and end parts) by conventional and high-resolution transmission electron microscopy. It was found that a band crystalline structure with a strongly crystallographic orientation was formed at the tip part, while inhomogeneous nanocrystallization occurred in the middle parts, and the amorphous structure remained almost unchanged in the end part. The different structures observed in different parts of the deformed sample are attributed to the inhomogeneous deformation of the BMG at high strain rates.