Newtonian flow and phase instability in a bulk metallic glass deformed in the supercooled liquid region

The deformation behavior of a bulk amorphous Zr-10Al-5Ti-l7.9Cu-14.6Ni alloy was studied in the supercooled liquid region. The alloy exhibits Newtonian behavior at low strain rates but to become non-Newtonian at high strain rates. X-ray diffraction and high-resolution electron microscopy results showed the presence of nanocrystallites in the deformed samples, suggesting the non-Newtonian behavior was actually associated with concurrent crystallization of the amorphous structure during deformation. A mechanistic model based upon structural evolution is offered to explain the observed non-Newtonian behavior.