Bulk metallic glasses (BMGs) can range from exceptionally tough to brittle depending on their structural state; however, quantifying their structure-property relationships has been an unresolved challenge. Our findings revealed that local hardness variations within the BMG microstructure strongly affect the fracture behavior. Moreover, the hardness heterogeneities are controlled by the size and volume fraction of FCC-like medium-range order (MRO) clusters. We have proposed a model of ductile phase softening whereby relatively soft FCC-like MRO clusters sit in a matrix of harder icosahedral dominated ordering, while micropillar compression testing has revealed how the activation of these clusters into shear transformation zones can be negatively affected by oxygen impurities which in turn lower the fracture toughness.
EXTENDED ABSTRACT