Ductile Bulk Metallic Glass

We report on experimental evidence of pronounced global plasticity measured in monolithic Pt_57.5Cu_14.7Ni_5.3P_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  MPa m^-1/2.