Influence of as-cast spherulites on the fracture toughness of a Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glass

This study addresses the influence of as-cast spherulites, which may be present in the glassy matrix of a bulk metallic glass owing to the processing conditions, on its fracture behaviour. The fracture toughness of a Zr₅₅Cu₃₀Al₁₀Ni₅ glass containing a low fraction as-cast spherulites (∼1% volume fraction) is investigated by means of bending tests. The resulting mode-I fracture toughness values, around 72 MPam, reveal the moderate detrimental effect of the spherulites. This result is compared to previous results for flawless and dendrite-containing glasses of the same composition, as well as with results from literature. The role played by the spherulites in crack propagation, under mode I and II, and fracture is finally addressed by means of fractography observations and finite element computations.