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Title: Lattice strain evolution and load partitioning during creep of a Ni-based superalloy single crystal with rafted γ′ microstructure

Abstract

In-situ neutron diffraction measurements were performed on monocrystalline samples of the Ni-based superalloy CMSX-4 during N-type γ' raft formation under the tensile creep conditions of 1150 °C/100 MPa, and subsequently on a rafted sample under the low temperature/high stress creep conditions of 715 °C/825 MPa. During 1150 °C/100 MPa creep, the γ' volume fraction decreased from ~70% to ~50%, the lattice parameter misfit was partly relieved, and the load was transferred from the creeping γ matrix to the γ' precipitates. On cooling back to room temperature, a fine distribution of γ' precipitates formed in the γ channels, and these precipitates were present in the 715 °C/825 MPa creep regime. Under low temperature/high stress creep, the alloy with rafted γ' microstructure exhibited superior creep strength to the cuboidal γ' microstructure produced following a standard heat-treatment. A lengthy creep incubation period was observed, believed to be associated with {111}$$\langle$$110$$\rangle$$ dislocations hindering propagation of {112}$$\langle$$110$$\rangle$$ dislocations. Following the creep incubation period, extensive macroscopic creep strain accumulated during primary creep as the γ phase yielded. Lastly, the diffraction data suggest a loss of precipitate/matrix coherency in the (0k0) interfaces as creep strain accumulated.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2];  [3];  [4];  [4];  [5]
  1. Northwestern Univ., Evanston, IL (United States); Univ. of Cambridge (United Kingdom)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Imperial College, London (United Kingdom)
  4. Northwestern Univ., Evanston, IL (United States)
  5. Univ. of Cambridge (United Kingdom)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
OSTI Identifier:
1559752
Alternate Identifier(s):
OSTI ID: 1550346
Grant/Contract Number:  
AC05-00OR22725; EP/M005607/1; EP/L001748/1
Resource Type:
Accepted Manuscript
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 135; Journal Issue: C; Journal ID: ISSN 1359-6454
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Coakley, James, Ma, Dong, Frost, Matthew, Dye, David, Seidman, David N., Dunand, David C., and Stone, Howard J. Lattice strain evolution and load partitioning during creep of a Ni-based superalloy single crystal with rafted γ′ microstructure. United States: N. p., 2017. Web. doi:10.1016/j.actamat.2017.06.021.
Coakley, James, Ma, Dong, Frost, Matthew, Dye, David, Seidman, David N., Dunand, David C., & Stone, Howard J. Lattice strain evolution and load partitioning during creep of a Ni-based superalloy single crystal with rafted γ′ microstructure. United States. doi:10.1016/j.actamat.2017.06.021.
Coakley, James, Ma, Dong, Frost, Matthew, Dye, David, Seidman, David N., Dunand, David C., and Stone, Howard J. Mon . "Lattice strain evolution and load partitioning during creep of a Ni-based superalloy single crystal with rafted γ′ microstructure". United States. doi:10.1016/j.actamat.2017.06.021. https://www.osti.gov/servlets/purl/1559752.
@article{osti_1559752,
title = {Lattice strain evolution and load partitioning during creep of a Ni-based superalloy single crystal with rafted γ′ microstructure},
author = {Coakley, James and Ma, Dong and Frost, Matthew and Dye, David and Seidman, David N. and Dunand, David C. and Stone, Howard J.},
abstractNote = {In-situ neutron diffraction measurements were performed on monocrystalline samples of the Ni-based superalloy CMSX-4 during N-type γ' raft formation under the tensile creep conditions of 1150 °C/100 MPa, and subsequently on a rafted sample under the low temperature/high stress creep conditions of 715 °C/825 MPa. During 1150 °C/100 MPa creep, the γ' volume fraction decreased from ~70% to ~50%, the lattice parameter misfit was partly relieved, and the load was transferred from the creeping γ matrix to the γ' precipitates. On cooling back to room temperature, a fine distribution of γ' precipitates formed in the γ channels, and these precipitates were present in the 715 °C/825 MPa creep regime. Under low temperature/high stress creep, the alloy with rafted γ' microstructure exhibited superior creep strength to the cuboidal γ' microstructure produced following a standard heat-treatment. A lengthy creep incubation period was observed, believed to be associated with {111}$\langle$110$\rangle$ dislocations hindering propagation of {112}$\langle$110$\rangle$ dislocations. Following the creep incubation period, extensive macroscopic creep strain accumulated during primary creep as the γ phase yielded. Lastly, the diffraction data suggest a loss of precipitate/matrix coherency in the (0k0) interfaces as creep strain accumulated.},
doi = {10.1016/j.actamat.2017.06.021},
journal = {Acta Materialia},
number = C,
volume = 135,
place = {United States},
year = {2017},
month = {6}
}

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