Role of free volume in strain softening of as-cast and annealed bulk metallic glass

Byung Gil Yoo, Kyoung Won Park, Jae-chul Lee, U. Ramamurty, Jae Il Jang

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Plasticity in amorphous alloys is associated with strain softening, induced by the creation of additional free volume during deformation. In this paper, the role of free volume, which was a priori in the material, on work softening was investigated. For this, an as-cast Zr-based bulk metallic glass (BMG) was systematically annealed below its glass transition temperature, so as to reduce the free volume content. The bonded-interface indentation technique is used to generate extensively deformed and well defined plastic zones. Nanoindentation was utilized to estimate the hardness of the deformed as well as undeformed regions. The results show that the structural relaxation annealing enhances the hardness and that both the subsurface shear band number density and the plastic zone size decrease with annealing time. The serrations in the nanoindentation load-displacement curves become smoother with structural relaxation. Regardless of the annealing condition, the nanohardness of the deformed regions is ∼12-15% lower, implying that the prior free volume only changes the yield stress (or hardness) but not the relative flow stress (or the extent of strain softening). Statistical distributions of the nanohardness obtained from deformed and undeformed regions have no overlap, suggesting that shear band number density has no influence on the plastic characteristics of the deformed region.

Original languageEnglish
Pages (from-to)1405-1416
Number of pages12
JournalJournal of Materials Research
Volume24
Issue number4
DOIs
Publication statusPublished - 2009 Apr 1

Fingerprint

Free volume
Metallic glass
metallic glasses
plastic deformation
casts
Nanohardness
Structural relaxation
hardness
plastics
Shear bands
Hardness
Nanoindentation
Annealing
Plastics
nanoindentation
annealing
work softening
shear
Amorphous alloys
statistical distributions

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanical Engineering
  • Mechanics of Materials
  • Condensed Matter Physics

Cite this

Role of free volume in strain softening of as-cast and annealed bulk metallic glass. / Yoo, Byung Gil; Park, Kyoung Won; Lee, Jae-chul; Ramamurty, U.; Jang, Jae Il.

In: Journal of Materials Research, Vol. 24, No. 4, 01.04.2009, p. 1405-1416.

Research output: Contribution to journalArticle

Yoo, Byung Gil ; Park, Kyoung Won ; Lee, Jae-chul ; Ramamurty, U. ; Jang, Jae Il. / Role of free volume in strain softening of as-cast and annealed bulk metallic glass. In: Journal of Materials Research. 2009 ; Vol. 24, No. 4. pp. 1405-1416.
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