Compressive plasticity and toughness of a Ti-based bulk metallic glass

The effects of changes in sample dimensions on the compressive plasticity and fracture toughness/energy have been determined for Ti40Zr25Cu12Ni3Be20 bulk metallic glass (BMG). Changes in sample dimensions alone produced widely different values for compressive plasticity. While these were correlated with changes to the measured Poisson's ratio for samples of the same composition cast into different sample sizes, significant effects or testing conditions apart from the Poisson's ratio on the measured compressive plasticity are also demonstrated. Fracture toughness testing oil the same material/size that exhibited zero compressive plasticity produced both notch and fatigue pre-cracked toughness in excess of 100 MPa m(1/2), while a size effect on the magnitude of toughness was similarly demonstrated. Discussions on the source(s) of the size effect on toughness are provided in addition to demonstrating that exceptional toughness can be obtained in this BMG which exhibits essentially zero compressive plasticity under certain test conditions. The apparent critical Poisson's ratio for plasticity/toughness is thus different in these very different types of tests. (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.