Characterization and modeling of deformation mechanisms in Ni-base superalloy 718

D. McAllister, D. Lv, L. Feng, H. Deutchman, A. Wessman, Y. Wang, M. J. Mills

Research output: Chapter in Book/Report/Conference proceedingConference contribution

6 Scopus citations

Abstract

Although the relationships between processing and the resulting properties are relatively well known for alloy 718, a better understanding of the deformation mechanisms activated across its usable temperature range is needed to create more mechanistically accurate property models. In this work, direct atomic-scale imaging with high angle annular dark field scanning transmission electron microscopy (STEM) has been complemented by phase field modeling informed by generalized stacking fault surface calculations using density functional theory. This coupled experiment/modeling approach has shed light on the complex shearing processes occurring in alloy 718 following a standard commercial heat treatment, which produces both monolithic y and y" particles, as well as composite particles. Deformation at room temperature occurs through complex shearing of γ" into intrinsic stacking fault configurations that were restricted to the precipitates. Exploration of possible shearing sequences with the aide of phase-field dislocation dynamics has revealed that precipitate shearing by motion of coupled 1/2<110> dislocations of non-parallel Burgers vectors on the {111} glide plane is the dominant deformation mechanism at lower temperature. A “fast-acting” yield strength model is discussed which takes into account microstructure variations and deformation mechanism transitions. Deformation at higher temperature (427 and 649 °C) has revealed a distinct transition in deformation modes, including stacking faults extending into the matrix, as well as microtwinning. The possible origin of the temperature and rate dependence of the stacking fault and microtwinning modes and temperature will be discussed.

Original languageEnglish (US)
Title of host publicationProceedings of the 9th International Symposium on Superalloy 718 and Derivatives
Subtitle of host publicationEnergy, Aerospace, and Industrial Applications
EditorsChantal Sudbrack, Kevin Bockenstedt, Max Kaplan, Zhongnan Bi, Paul Jablonski, Joel Andersson, Jon Groh, Eric Ott, Xingbo Liu, Daisuke Nagahama, Ian Dempster, Karl Heck
PublisherSpringer International Publishing
Pages319-338
Number of pages20
ISBN (Electronic)9783319894799
DOIs
StatePublished - 2018
Externally publishedYes
Event9th International Symposium on Superalloy 718 and Derivatives: Energy, Aerospace, and Industrial Applications - Pittsburgh, United States
Duration: Jun 3 2018Jun 6 2018

Publication series

NameMinerals, Metals and Materials Series
Volume2018-June
ISSN (Print)2367-1181
ISSN (Electronic)2367-1696

Conference

Conference9th International Symposium on Superalloy 718 and Derivatives: Energy, Aerospace, and Industrial Applications
Country/TerritoryUnited States
CityPittsburgh
Period6/3/186/6/18

Keywords

  • Characterization
  • Phase field modelling
  • STEM

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy Engineering and Power Technology
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry

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