The effects of mixed mode loading on the fracture behavior of Zr-based bulk metallic glasses (BMGs) (Vitreloy I and Vitreloy 106) were investigated. Mixed mode I/II and mixed mode I/III fracture conditions were tested using both notched and fatigue-precracked specimens. Fully amorphous samples exhibited tremendous increases in fracture energy with the application of mixed mode loading, while partially crystalline samples exhibited more modest increases. A comparison to the behavior of other material systems (e.g., polymers, ceramics, crystalline metals, and composites) illustrates the tremendous increase in fracture energy exhibited by these BMGs under mixed mode loading conditions.

The effects of changes in notch radius on the toughness of two different Zr-based bulk metallic glasses have been determined. It is shown that increases in notch radius produce large increases to the toughness, accompanied by extensive shear banding and crack bifurcation. The fracture toughness of twenty (20) fatigue precracked specimens exhibiting planar crack growth were in the range 20.3 ± 6.7 MPa√m for the two Zr-based glasses. Increasing the notch radius to 110 μm produced notch toughness in the range 95.3 ± 8.3 MPa√m for nine (9) tests on Vitreloy I, well in excess of that typically observed in most structural materials. Toughness tests conducted on two fatigue precracked specimens of Vitreloy I at 77 K produced values for fracture toughness that were in the range 17.9 ± 2.7 MPa√m, similar to that obtained at 298 K. The fatigue precracked fracture toughness of metallic glass composites containing large crystalline regions of a body centered cubic Zr-Ti-Nb alloy were in the range 29–42 MPa√m, but the values were temperature dependent over the range 148 K to 500 K. Fracture surfaces were analyzed via Scanning Electron Microscopy (SEM).

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