Poisson’s Ratio and Intrinsic Plasticity of Metallic Glasses

Abstract

Through a comparison of the activation barrier densities for plastic deformation and brittle fracture at the yield point, a condition for intrinsic plasticity versus brittleness of metallic glasses under shear loading is derived. The quantitative role of Poisson’s ratio ν on fracture is revealed and additional effects due to local shear modulus (G) fluctuations are pointed out. The findings account for the onset of plasticity near reported ν values, as well as the brittleness of some high-ν alloys. Structural relaxation increases G and reduces fluctuations, incurring dual adverse effects on ductility. Implications for designing ductile metallic glasses are discussed.