Possible local superplasticity of amorphous metallic alloys in the catastrophic shear band under low temperature ductile shear failure

• Published in: Scripta materialia 1996-09, Vol.35 (6), p.781-784
• Main Authors: Bengus, V., Tabachnikova, E., Csach, K., Miškuf, J., Ocelík, V.
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Metals. Metallurgy; Physics
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/1359-6462(96)00209-6

The "vein pattern" (VP) formation on the failure surfaces is a characteristic feature of the low temperature ductile shear failure of amorphous alloys. Argon and Salama proposed the meniscus instability in the thin "liquid-like" layer (layer with a low viscosity) as a mechanism of the VP formation. This thin layer is formed along the catastrophic shear band due to the local adiabatic heating. Experimental observations of the density of veins on the fracture surface as a function of failure stress have shown that the state of this "liquid-like" layer is closer to the solid than to the liquid state due to the non-zero plastic resistance. Thus the layer can be considered as a solid with high plasticity (the average macroscopic plastic shear has been estimated to have the order of 10 exp 2 ). The real instant plasticity of the material in the liquid-like layer can be estimated from the plastic deformation localized in single veins. The veins usually lie on the failure surface. Their height has been reported close to 0.1-0.2 mu m. On the other hand in a number of amorphous alloys protruding veins are observed that are oriented oblique to the failure surface or even perpendicularly to it. In this work we have observed and estimated the magnitude of the plastic deformation in these protruding veins. This estimation has been realized by the fractographic analysis of fractured surfaces for various amorphous alloys.