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

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. The real instant plasticity of the material in the liquid-like layer can be estimated from the plastic deformation localized in single veins. In this work the authors 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. Failure surfaces after the low temperature (0.5--300 K) shear failure were observed using a TESLA BS-300 scanning electron microscope for various amorphous alloys deformed under uniaxial tension (Fe84B16 and Fe80B20 amorphous ribbons with the cross sections of 6.0 x 0.03 mm2, Pd84.5Si15.5 amorphous ribbon with cross section of 2 x 0.03 mm2) and under uniaxial compression (Cu50Zr35Ti8Hf5Ni2 amorphous rod with 3 mm diameter)