The role of thermal activation on dynamic stress-induced inelasticity and damage in Ti-6Al-4V

H. V. Arrieta, H. D. Espinosa*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Planar impact experiments are performed on preheated Ti-6Al-4V specimens, at temperatures in the range 25-550 °C, to determine the role of thermal activation on dynamic stress-induced inelasticity and damage. Measurements in this high temperature and high strain rate regime are made possible by modification of the standard plate impact facility to include heating capabilities. This paper describes in detail needed hardware and experimental procedure. A symmetric planar impact configuration is employed to achieve high compressive and tensile stresses in the specimens. The targets are heated by a magnetic field generated by current flow on a coil surrounding the specimen. Interferometric techniques are employed to record the free surface velocity of the target plates. The experimental results show that thermal activation overcomes the role of rate dependence in the material constitutive behavior. The Hugoniot elastic limit (HEL) and spall strength of Ti-6Al-4V significantly decrease with temperature despite the high strain rate, about 105s-1, used in the tests. The damage mechanism remains the same at high and room temperatures, i.e., microvoid nucleation, growth and coalescence. Microscopy studies, performed on recovered samples, show that temperature substantially reduces the strain inhomogeneity leading to microvoid formation and that a change in void nucleation site occurs. A completely reversible shock-induced phase transformation α→ω appears to be present in the tested Ti-6Al-4V. Evidence of this phase transformation is observed in the velocity histories upon unloading of the first compressive pulse. The phase transformation is controlled by a combination of thermal and stress driven mechanisms.

Original languageEnglish (US)
Pages (from-to)573-591
Number of pages19
JournalMechanics of Materials
Volume33
Issue number10
DOIs
StatePublished - Oct 1 2001

Keywords

  • Damage
  • Dynamic plasticity
  • Failure mechanisms
  • High temperature testing
  • Phase transformation
  • Spallation

ASJC Scopus subject areas

  • Materials Science(all)
  • Instrumentation
  • Mechanics of Materials

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