Low-temperature superplasticity of ultra-fine-grained Ti-6Al-4V processed by equal-channel angular pressing

  • Y. G. Ko
  • C. S. Lee
  • D. H. Shin
  • S. L. Semiatin


The low-temperature superplasticity of ultra-fine-grained (UFG) Ti-6Al-4V was established as a function of temperature and strain rate. The equiaxed-alpha grain size of the starting material was reduced from 11 to 0.3 µm (without a change in volume fraction) by imposing an effective strain of ∼4 via isothermal, equal-channel angular pressing (ECAP) at 873 K. The ultrafine microstructure so produced was relatively stable during annealing at temperatures up to 873 K. Uniaxial tension and load-relaxation tests were conducted for both the starting (coarse-grained (CG)) and UFG materials at temperatures of 873 to 973 K and strain rates of 5 × 10−5 to 10−2 s−1. The tension tests revealed that the UFG structure exhibited considerably higher elongations compared to those of the CG specimens at the same temperature and strain rate. A total elongation of 474 pct was obtained for the UFG alloy at 973 K and 10−4 s−1. This fact strongly indicated that low-temperature superplasticity could be achieved using an UFG structure through an enhancement of grain-boundary sliding in addition to strain hardening. The deformation mechanisms underlying the low-temperature superplasticity of UFG Ti-6Al-4V were also elucidated by the load-relaxation tests and accompanying interpretation based on inelastic deformation theory.


Material Transaction Total Elongation ECAP Pass Superplastic Defor 
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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2006

Authors and Affiliations

  • Y. G. Ko
    • 1
  • C. S. Lee
    • 1
  • D. H. Shin
    • 2
  • S. L. Semiatin
    • 3
  1. 1.the Department of Materials Science and EngineeringPohang University of Science and TechnologyPohangKorea
  2. 2.the Department of Metallurgy and Materials ScienceHanyang UniversityGyeonggi-DoKorea
  3. 3.the Air Force Research LaboratoryAFRL/MLLMWright-Patterson AFB

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