Ductile Bulk Metallic Glass

We report on experimental evidence of pronounced global plasticity measured in monolithic ${\mathrm{P}\mathrm{t}}_{57.5}{\mathrm{C}\mathrm{u}}_{14.7}{\mathrm{N}\mathrm{i}}_{5.3}{\mathrm{P}}_{22.5}$ bulk metallic glass under both bending and unconfined compression loading conditions. A plastic strain of 20% is measured, never before seen in metallic glasses. Also, permanent deformation and a strain exceeding 3% before failure is observed during bending of 4 mm thick samples. To date, no monolithic metallic material has exhibited such a combination of high strength, extensive ductility, and high elastic limit. The large plasticity is reflected in a high Poisson ratio of 0.42, which causes the tip of a shear band to extend rather than initiate a crack. This results in the formation of multiple shear bands and is the origin of the observed large global ductility and very high fracture toughness, approximately $80\mathrm{M}\mathrm{P}\mathrm{a}{\mathrm{m}}^{-1/2}$.