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铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 12    No. 4    August 2002

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Deformation of metallic glasses with special
emphasis in supercooled liquid region
T.G.Nieh

Lawrence Livermore National Laboratory, L-350, PO Box 808,
Livermore, CA 94551, USA

Abstract:Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous deformation begins to take place. A bulk amorphous Zr-10Al-5Ti-17.9Cu-14.6Ni alloy was observed to exhibit the Newtonian behavior at low strain rates but becomes n on-Newtonian at high strain rates in the supercooled liquid region. Structures of the amorphous material, both before and after deformation, were examined using X-ray diffraction and high-resolution electron microscopy. Results showed the presence of nanocrystallites in the deformed samples. Thus, the non-Newtonian behavior is attributable to the concurrent crystallization of the amorphous structure during deformation. A mechanistic model is presented to interpret the observed non-Newtonian result. A phenomenological approach is also used to develop the deformation map for bulk metallic glasses in the supercooled liquid region.

 

Key words: metallic glass; viscous flow; superplasticity; dynamic crystallization; amorphous alloys; Newtonian flow

ISSN 1672-7029
CN 43-1423/U

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