Role of the secondary phase η during high temperature compression of ATI 718PlusR

Christiane Kienl, Paranjayee Mandal, Himanshu Lalvani, Catherine M. F. Rae

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Abstract

High-temperature compression tests were performed on a Ni-base superalloy with a multi-phase microstructure. Particular attention was given on the influence of the η phase on recrystallization of ATI 718Plus®. The compression tests were performed at two temperatures over a variety of strains and strain rates. Meta-dynamic recrystallization was studied by exposing the samples to a set dwell time at the test temperature after deformation. Electron backscatter diffraction (EBSD) was used to investigate the microstructures after the tests. Secondary electron imaging (SEI) and scanning transmission electron microscopy (STEM) were utilized in order to investigate the deformation behavior of η and obtaining a detailed understanding of the recrystallization mechanism. The secondary η phase was found to increase the recrystallized fraction compared to η free tests. However, clusters of thin lamellar η inhibited recrystallization. The flow curve softening was distinctly stronger in the microstructure containing precipitates. It could be shown by SE images that this was due to the breakage and realignment of η. In addition, η was also found to accommodate the stresses by a remarkable deformation without breaking up. This was considered to be due to the composite nature of the precipitate as well as the ongoing recrystallization in the surrounding matrix.

Original languageEnglish
Pages (from-to)4008-4021
Number of pages14
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume51
Issue number8
Early online date30 May 2020
DOIs
Publication statusPublished - 1 Aug 2020

Keywords

  • two phase microstructure
  • superalloy
  • high temperature compression
  • deformation twinning

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