On the formation of an ultrafine-duplex structure facilitated by severe shear deformation in a Ti-20Mo β-type titanium alloy

W. Xu*, X. Wu, M. Stoica, M. Calin, U. Kühn, J. Eckert, K. Xia

*Corresponding author for this work

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Severe plastic deformation in the form of equal channel angular pressing (ECAP) has been adopted to introduce severe shear strain into a Ti-20 wt.% Mo β-type titanium alloy to elucidate the aging response of the severely deformed β matrix. Upon isothermal aging in the (α + β) phase field, selective heterogeneous α nucleation and growth resulted in a mixed precipitation microstructure. An ultrafine-duplex (α + β) structure composed of equiaxed α precipitates formed inside the shear bands (SBs) created during ECAP, whereas acicular α precipitates were favoured outside the SBs. This distinct precipitation structure has been correlated to the structural characteristics of the SBs: high disorder with dislocation cells characteristic of low-angle boundaries and enhanced atomic diffusivity. The highly disordered structure results in a weak variant selection and thereby promotes randomly orientated α precipitation without obeying the Burgers orientation relationship. Furthermore, the enhanced atomic diffusivity facilitates rapid growth of the α nuclei to form the ultrafine-duplex (α + β) structure.

Original languageEnglish
Pages (from-to)5067-5078
Number of pages12
JournalActa Materialia
Volume60
Issue number13-14
DOIs
Publication statusPublished - Aug 2012
Externally publishedYes

Keywords

  • β titanium alloy
  • Precipitation
  • Severe plastic deformation
  • Shear bands
  • Ultrafine-grained materials

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