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:

Coakley, James  ^[1];

• Search DOE PAGES for author "Coakley, James"
• Search DOE PAGES for ORCID "0000-0003-1360-0649"

Ma, Dong  ^[2];

• Search DOE PAGES for author "Ma, Dong"
• Search DOE PAGES for ORCID "0000-0003-3154-2454"

Frost, Matthew  ^[2];

• Search DOE PAGES for author "Frost, Matthew"
• Search DOE PAGES for ORCID "0000-0001-6821-170X"

Dye, David ^[3]; Seidman, David N. ^[4]; Dunand, David C. ^[4]; Stone, Howard J. ^[5]

---

+ Show Author Affiliations

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:

Mon Jun 12 00:00:00 EDT 2017

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); 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