Unusual brittle behavior of Pd-based bulk metallic glass

The bending plasticity of Pd-based and Pt-based bulk metallic glasses (BMGs) is compared. Low cooling rates obtained during bulk casting render Pd–BMG (Pd 43Cu 27Ni 10P 20) brittle, whereas Pt–BMG (Pt 57.5Cu 14.7Ni 5.3P 22.5) retains high plasticity at all cooling rates. The ratio of the shear modulus ( G) to the bulk modulus ( B) in the two alloys is similar (∼0.2). A previously proposed critical G/ B value of 0.41 for tough to brittle transition is not supported by our findings, which rather suggest an alloy specific critical G/ B.