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Title: Dislocation decorrelation and relationship to deformation microtwins during creep of a precipitate strengthened Ni-based superalloy

Abstract

The evolution of microtwins during high temperature creep deformation in a strengthened Ni-base superalloy has been investigated through a combination of creep testing, transmission electron microscopy (TEM), theoretical modeling, and computer simulation. Experimentally, microtwin nucleation sources were identified and their evolution was tracked by characterizing the deformation substructure at different stages of creep deformation. Deformation is highly localized around stress concentrators such as carbides, borides and serrated grain boundaries, which act as sources of a/2<110> matrix-type dislocations. Due to fine channels between particles, coupled with the low matrix stacking fault energy, the a/2<110> matrix dislocations dissociate into a/6<112> Shockley partials, which were commonly observed to be decorrelated from one another, creating extended intrinsic stacking faults in the matrix. Microtwins are common and form via Shockley partial dislocations cooperatively shearing both and phases on adjacent {111} glide planes. The TEM observations lead directly to an analysis of dislocation-precipitate interactions. Through phase field simulations and theoretical analyses based on Orowan looping, the important processes of dislocation dissociation and decorrelation are modeled in detail, providing comprehensive insight into the microstructural features and applied stress conditions that favor the microtwinning deformation mode in strengthened Ni-based superalloys.

Authors:
 [1];  [2];  [3];  [4];  [2];  [2]
  1. ORNL
  2. Ohio State University
  3. Pacific Northwest National Laboratory (PNNL)
  4. GE Global Research
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1025392
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 59; Journal Issue: 19; Journal ID: ISSN 1359-6454
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BORIDES; CARBIDES; COMPUTERIZED SIMULATION; CONCENTRATORS; CREEP; DEFORMATION; DISLOCATIONS; DISSOCIATION; GRAIN BOUNDARIES; HEAT RESISTING ALLOYS; NUCLEATION; SIMULATION; STACKING FAULTS; TESTING; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Unocic, Raymond R, Zhou, Ning, Kovarik, Libor, Shen, Chen, Wang, Yunzhi, and Mills, Michael J. Dislocation decorrelation and relationship to deformation microtwins during creep of a precipitate strengthened Ni-based superalloy. United States: N. p., 2011. Web. doi:10.1016/j.actamat.2011.07.069.
Unocic, Raymond R, Zhou, Ning, Kovarik, Libor, Shen, Chen, Wang, Yunzhi, & Mills, Michael J. Dislocation decorrelation and relationship to deformation microtwins during creep of a precipitate strengthened Ni-based superalloy. United States. https://doi.org/10.1016/j.actamat.2011.07.069
Unocic, Raymond R, Zhou, Ning, Kovarik, Libor, Shen, Chen, Wang, Yunzhi, and Mills, Michael J. 2011. "Dislocation decorrelation and relationship to deformation microtwins during creep of a precipitate strengthened Ni-based superalloy". United States. https://doi.org/10.1016/j.actamat.2011.07.069.
@article{osti_1025392,
title = {Dislocation decorrelation and relationship to deformation microtwins during creep of a precipitate strengthened Ni-based superalloy},
author = {Unocic, Raymond R and Zhou, Ning and Kovarik, Libor and Shen, Chen and Wang, Yunzhi and Mills, Michael J.},
abstractNote = {The evolution of microtwins during high temperature creep deformation in a strengthened Ni-base superalloy has been investigated through a combination of creep testing, transmission electron microscopy (TEM), theoretical modeling, and computer simulation. Experimentally, microtwin nucleation sources were identified and their evolution was tracked by characterizing the deformation substructure at different stages of creep deformation. Deformation is highly localized around stress concentrators such as carbides, borides and serrated grain boundaries, which act as sources of a/2<110> matrix-type dislocations. Due to fine channels between particles, coupled with the low matrix stacking fault energy, the a/2<110> matrix dislocations dissociate into a/6<112> Shockley partials, which were commonly observed to be decorrelated from one another, creating extended intrinsic stacking faults in the matrix. Microtwins are common and form via Shockley partial dislocations cooperatively shearing both and phases on adjacent {111} glide planes. The TEM observations lead directly to an analysis of dislocation-precipitate interactions. Through phase field simulations and theoretical analyses based on Orowan looping, the important processes of dislocation dissociation and decorrelation are modeled in detail, providing comprehensive insight into the microstructural features and applied stress conditions that favor the microtwinning deformation mode in strengthened Ni-based superalloys.},
doi = {10.1016/j.actamat.2011.07.069},
url = {https://www.osti.gov/biblio/1025392}, journal = {Acta Materialia},
issn = {1359-6454},
number = 19,
volume = 59,
place = {United States},
year = {Sat Jan 01 00:00:00 EST 2011},
month = {Sat Jan 01 00:00:00 EST 2011}
}