Shear band mechanics in metallic plates: the Poisson’s effect and strength softening
Yujie Wei (Institute of Mechanics, Chinese Academy of Sciences), Xianqi Lei (), Wei-Hua Wang (), A. Greer ()
Plasticity at Different Length Scales
Mon 10:45 - 12:15
CIT 219
We develop a quantitative analysis of how the plastic deformation in a metallic glass is more uniform if its Poisson ratio \nu is higher. The plasticity of metallic glasses under ambient conditions is mediated by shear localized in thin bands, and can be characterized by experiments on the bending of thin plates. We extend the analysis by Conner et al. (Conner et al., J. Appl. Phys. 94 (2003), 904–911) of bands in bent plates to include the micromechanics of individual shear bands. Expressions are derived for the shear band spacing and the offset on each band. Both these quantities are predicted to decrease as \nu is increased. The predictions are tested against measurements on metallic glasses with a wide range of \nu. Good agreement is found, supporting the new model for the shear-band spacing, and pointing the way towards more diffuse deformation, and consequently improved plasticity and toughness, of metallic glasses as n increases toward the limiting value of 0.5. In addition, by applying a combination of micro-scale bending with in situ tensile tests, we successfully determine the strength at SBs in two typical Zr41Ti14Cu12.5Ni10Be22.5 and (Cu50Zr50)95Al5 MGs. We find that the strengths at SBs are about 20% lower than those of their respective intact counterparts. We notice, based on fractographic examinations, that stable SBs may only induce negligible heat, but unstable SBs give rise to high temperature rise in SBs. This observation sheds light on the controversy about whether SBs at MGs must be hot.