Structure transformation and fractography in Zr20Ti20Cu20Ni20Be20 metallic glass

In this paper, the structure transformation and fractography of a metallic glass Zr20Ti20Cu20Ni20Be20 (at.%) are investigated. As measured in a previous study, this metallic glass exhibits three exothermic events during heating at 20 K/min in differential scanning calorimetry. However, based on the observation by transmission electron microscope, the first exothermic event is found not to correspond to the crystallization behavior but the structural relaxation, the precipitation of crystalline phase happens to the second one, and the nano-scale crystalline particles coarsen during the third one. On the other hand, although the as-cast Zr20Ti20Cu20Ni20Be20 metallic glass fractures in an extremely brittle way in compression tests, the fractograph shows two types of features: One is mirror-like smoothness as an indicator of brittleness, and the other is vein-like pattern as a sign of plasticity. These different features are attributed to the fracture mode instead of the plasticity or toughness in metallic glass.