Self-organized, size-selection of precipitates during severe plastic deformation of dilute Cu-Nb alloys at low temperatures

J. A. Beach, M. Wang, P. Bellon, S. Dillon, Yu Ivanisenko, T. Boll, R. S. Averback

Research output: Contribution to journalArticle

Abstract

High pressure torsion (HPT) experiments have been carried out at very low temperatures (−78 °C) on dilute Cu-Nb alloys. The samples were prepared by magnetron sputtering to create solid solutions containing nominally between 1 at.% and 10 at.% Nb. Some samples were pre-annealed to 700 °C to form large Nb precipitates, ∼75 nm in radius, prior to HPT. For the unannealed alloys, HPT at low temperatures led to alloy decomposition for alloys with concentrations greater than ∼2 at.% Nb, with the steady state concentration of Nb increasing from ∼1.5 to ∼3 at.% as the initial concentration of Nb was increased. It was also observed that BCC Nb precipitates formed during low-temperature HPT, with a steady state precipitate size ∼10 nm in radius, which was insensitive to alloy concentration. HPT of pre-annealed Cu-10 at.% alloy led to the same steady state microstructure as the unannealed sample, indicating that the steady state during the low temperature HPT process is independent of the initial state for these Cu-Nb alloys. A model for phase evolution in strongly immiscible alloys during severe, low-temperature deformation is offered and implemented through kinetic Monte Carlo simulations. Good agreement with experiment is obtained.

Original languageEnglish (US)
Pages (from-to)217-223
Number of pages7
JournalActa Materialia
Volume140
DOIs
StatePublished - Nov 2017

Keywords

  • Copper-niobium alloy
  • High pressure torsion
  • Self-organization
  • Severe plastic deformation
  • Shear induced mixing

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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