Hardness and shear band evolution in bulk metallic glasses after plastic deformation and annealing

Strain-induced hardening and annealing-induced softening are typical in crystalline metals. Bulk metallic glasses (BMG) exhibit the opposite behavior, namely, strain-induced softening and annealing-induced hardening. In addition, reversible softening–hardening–softening occurs in a BMG subjected to...

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Bibliographic Details
Published in:Acta materialia 2008-10, Vol.56 (18), p.5202-5213
Main Authors: Xie, S., George, E.P.
Format: Article
Language:English
Subjects:
Amorphous materials
ANNEALING
Applied sciences
COMPRESSION
DEFORMATION
DISTRIBUTION
Exact sciences and technology
HARDENING
HARDNESS
MATERIALS SCIENCE
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
METALLIC GLASSES
Metals. Metallurgy
MIXTURES
Plastic deformation
PLASTICS
SHEAR
Shear bands
Slip bands
Softening
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Summary:Strain-induced hardening and annealing-induced softening are typical in crystalline metals. Bulk metallic glasses (BMG) exhibit the opposite behavior, namely, strain-induced softening and annealing-induced hardening. In addition, reversible softening–hardening–softening occurs in a BMG subjected to a three-step deformation–annealing–deformation process. The hardness changes after deformation and annealing can be correlated with the shear band patterns around/underneath Vickers indents. Shear bands produced during indentation of as-cast BMG are semicircular and radial, consistent with the stress distribution beneath the indenter. In contrast, the shear bands in the pre-strained BMG are irregular and convoluted, and appear to be a mixture of the shear bands produced during the prior compression and those in the as-cast BMG. After annealing, the shear bands tend to recover their semicircular and radial shapes consistent with the annealing-induced hardening.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2008.07.009