Initiation and early stages of cavity growth during superplastic and hot deformation

A. K. Ghosh, DongHyun Bae, S. L. Semiatin

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

The formation and growth of internal voids in metallic alloys are of considerable concern in components produced by superplastic and hot forming processes. Grain boundary cavitation, observed under conditions where boundaries are weaker than grain interior, results from concentration of strain around non-deformable particles and hard second phases located at grain boundaries. Careful examination of microstructures of aluminum and titanium alloys show that most voids are "nucleated" due to incompatible deformation between phases, although a few cavities might preexist in certain alloys. Increased levels of local hydrostatic stress arising from plastic constraints can activate growth of interfacial defects leading to rapid dilatation, followed by a slower growth rate due to reduced constraint as voids expand. An interface-constrained plasticity growth model described in this work explains why cavity growth rate is enhanced by increased strain rate, larger particle size, decreasing forming temperature and lower m value (strain rate sensitivity parameter) in metals, not by the diffusional growth mechanism. Experimental studies, utilizing image analysis revealed how the population of cavity nuclei also increase with increasing strain, strain rate and decreasing temperature, supporting the predictions of this new model.

Original languageEnglish
Pages (from-to)609-616
Number of pages8
JournalMaterials Science Forum
Volume304-306
Publication statusPublished - 1999 Dec 1

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Superplastic deformation
Hot working
Strain rate
cavities
strain rate
voids
Grain boundaries
grain boundaries
superplastic forming
Titanium alloys
Cavitation
Image analysis
Plasticity
hot working
Aluminum alloys
Metals
Particle size
titanium alloys
Boundary conditions
Plastics

All Science Journal Classification (ASJC) codes

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

Cite this

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Initiation and early stages of cavity growth during superplastic and hot deformation. / Ghosh, A. K.; Bae, DongHyun; Semiatin, S. L.

In: Materials Science Forum, Vol. 304-306, 01.12.1999, p. 609-616.

Research output: Contribution to journalArticle

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