Compressive fracture morphology and mechanism of metallic glass

We quantitatively investigated the fracture morphologies of Zr52.5Cu17.9Ni14.6Al10Ti5 and Pd78Cu6Si16 metallic glasses (MGs) under compression. The characteristic features of the compressive fracture morphology were captured, and the shear vein patterns were found to be not a one-to-one correspondence between two opposing fracture surfaces in an identical sample. This finding experimentally confirms that the compressive failure behaves in a fracture mode of pure shear (mode II). Quantitative measurements show that a similar to 1 mu m thickness layer with materials not only inside but also adjacent to the major shear band contributes to the formation of shear vein patterns. The critical shear strain to break a shear band was found to be more than 10(5)% and higher in more ductile MGs under compression than tension. Estimation on the temperature rise at the fracture moment indicates that only similar to 5% of the total elastic energy stored in the sample converts into the heat required for melting the layer to form the vein patterns. The mode II fracture toughness was also estimated based on the quantitative measurements of shear vein pattern and found larger than the mode I fracture toughness. Finally, the deformation and fracture mechanisms of MGs under tension and compression were compared and discussed. These results may improve the understanding on the fracture behaviors and mechanisms of MGs and may provide instructions on future design for ductile MGs with high resistance for fracture. (C) 2013 AIP Publishing LLC.