Effects of open-volume regions on relaxation time-scales and fracture behavior of a Zr-Ti-Ni-Cu-Be bulk metallic glass

The plane strain fracture toughness of a Zr-Ti-Ni-Cu-Be bulk metallic glass was found to be significantly degraded after annealing at 300 degreesC. The fracture morphology was changed from characteristic vein patterns to cleavage-like features with little evidence of plasticity. Positron annihilation spectroscopy results revealed that atomic scale open-volume regions were reduced by annealing. A dynamic mechanical analysis showed that the atomic arrangement process for viscous flow was retarded as a result of annealing. The observed annealing embrittlement is ascribed to the loss of stress relief by viscous flow at the crack tip that results from the anneal-out of open-volume regions (C) 2003 Elsevier Science B.V. All rights reserved.