Plasticity-induced nanocrystallization in a Zr65Cu35 thin film metallic glass

The plasticity-induced nanocystalline phase transformation in the Zr65Cu35 thin film metallic glass (TFMG) was examined. A Zr65Cu35 film was synthesized by direct current magnetron sputtering. The metallic glass phase of the Zr65Cu35 film was confirmed by X-ray diffraction and high resolution transmission electron microscopy (HR-TEM). The Zr65Cu35 TFMG was deformed by micro Knoop indentation, and approximately 60% of the film thickness was deformed plastically. The formation of shear bands was observed at the edge of the indentation impressions. HR-TEM showed that nanocrystallization occurred only in the vicinity of the step-like shear bands formed at the edge of the indentation impression. No phase transformation was observed in other places, such as under the heavily deformed center area of the indentation impressions. The distinctive nanocrystallization observed in the Zr65Cu35 TFMG was explained in terms of the enhanced atomic mobility by severe localized plastic deformation of the shear bands.