Microstructural transformation in a ${\mathrm{Zr}}_{41}{\mathrm{Ti}}_{14}{\mathrm{Cu}}_{12.5}{\mathrm{Ni}}_{10}{\mathrm{Be}}_{22.5}$ bulk metallic glass under high pressure

The microstructure and its evolution of a ${\mathrm{Zr}}_{41}{\mathrm{Ti}}_{14}{\mathrm{Cu}}_{12.5}{\mathrm{Ni}}_{10}{\mathrm{Be}}_{22.5}$ bulk metallic glass (BMG) annealed under high pressure and below glass transition temperature are investigated by using high resolution transmission electron microscope, differential scanning calorimeter, x-ray diffraction, ultrasonic study, and density measurements. It is found that high pressure annealing below $T_g$ results in a microstructural transformation from short-range order to medium-range order in the BMG; the BMG with medium-range order structure exhibits different structural, thermal and acoustic properties.