Structural defects in Tini-based alloys after warm ECAP

Aleksandr Lotkov, Anatoly Baturin, Vladimir Kopylov, Victor Grishkov, Roman Laptev

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The microstructure, martensitic transformations and crystal structure defects in the Ti50Ni47.3Fe2.7 (at%) alloy after equal-channel angular pressing (ECAP, angle 90°, route BC, 1–3 passes at T = 723 K) have been investigated. A homogeneous submicrocrystalline (SMC) structure (grains / subgrains about 300 nm) is observed after 3 ECAP passes. Crystal structure defects in the Ti49.4Ni50.6 (at%) alloy (8 ECAP passes, angle 120°, BC route, T = 723 K, grains/subgrains about 300 nm) and Ti50Ni47.3Fe2.7 (at%) alloy with SMC B2 structures after ECAP were studied by positron lifetime spectroscopy at the room temperature. The single component with the positron lifetime τ1 = 132 ps and τ1 = 140 ps were observed for positron lifetime spectra (PLS) obtained from ternary and binary, correspondingly, annealed alloys with coarse-grained structures. This τ1 values correspond to the lifetime of delocalized positrons in defect-free B2 phase. The two component PLS were found for all samples exposed by ECAP. The component with τ2 = 160 ps (annihilation of positrons trapped by dislocations) is observed for all samples after 1–8 ECAP passes. The component with τ3 = 305 ps (annihilation of positrons trapped by vacancy nanoclusters) was detected only after the first ECAP pass. The component with τ3 = 200 ps (annihilation of positrons trapped by vacancies in the Ti sublattice of B2 structure) is observed for all samples after 3–8 ECAP passes.

Original languageEnglish
Article number1154
Pages (from-to)1-12
Number of pages12
JournalMetals
Volume10
Issue number9
DOIs
Publication statusPublished - Sep 2020

Keywords

  • Dislocations
  • ECAP
  • Microstructure
  • Nanoclusters
  • Positron lifetime spectroscopy
  • TiNi-based alloys
  • Vacancies

ASJC Scopus subject areas

  • Materials Science(all)

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