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Title: Creep-behavior modeling of the single-crystal superalloy CMSX-4

Abstract

An investigation has been undertaken into the creep behavior of the single-crystal superalloy CMSX-4. Creep deformation in the alloy occurs largely through dislocation activity in the {gamma} channels. Shearing of the {gamma}{prime} dislocations is observed, but at higher temperatures, this does not occur until late in life via the passage of superpartial dislocation pairs. At lower temperatures (1023 K) and high stress levels, shearing of the {gamma}{prime} precipitates is observed relatively early in the creep curve through the passage of {r_brace}111{l_brace}{l_angle}112{r_angle} dislocations, which leave superlattice stacking faults (SSFs) in the precipitates. The stress-rupture behavior of CMSX-4 has been modeled using a damage-mechanics technique, where the level of damage required to cause failure is defined by the effective stress reaching the material's ultimate tensile strength (UTS). This technique ensures that short-term rupture data extrapolate back to the UTS. High-temperature steady-state and tertiary creep are modeled using modified damage-mechanics equations, where the strain and damage rates are similar functions of stress. At intermediate operating temperatures of 1,023 and 1,123 K, the material exhibits pronounced sigmoidal primary creep of up to 4% strain, which cannot be modeled using a conventional approach. This transient behavior has been explained by the effect of internal stressesmore » acting on dislocations in the gamma matrix; such an internal stress has been included in the creep law and evolves as a function of the damage-state variable.« less

Authors:
;
Publication Date:
Research Org.:
Univ. of Cambridge (GB)
OSTI Identifier:
20075682
Alternate Identifier(s):
OSTI ID: 20075682
Resource Type:
Journal Article
Journal Name:
Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science
Additional Journal Information:
Journal Volume: 31; Journal Issue: 5; Other Information: PBD: May 2000; Journal ID: ISSN 1073-5623
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CREEP; NICKEL BASE ALLOYS; MONOCRYSTALS; MATHEMATICAL MODELS; DISLOCATIONS; PRECIPITATION; STRESSES; TEMPERATURE RANGE 1000-4000 K; DAMAGE

Citation Formats

MacLachlan, D.W., and Knowles, D.M. Creep-behavior modeling of the single-crystal superalloy CMSX-4. United States: N. p., 2000. Web. doi:10.1007/s11661-000-0258-0.
MacLachlan, D.W., & Knowles, D.M. Creep-behavior modeling of the single-crystal superalloy CMSX-4. United States. doi:10.1007/s11661-000-0258-0.
MacLachlan, D.W., and Knowles, D.M. Mon . "Creep-behavior modeling of the single-crystal superalloy CMSX-4". United States. doi:10.1007/s11661-000-0258-0.
@article{osti_20075682,
title = {Creep-behavior modeling of the single-crystal superalloy CMSX-4},
author = {MacLachlan, D.W. and Knowles, D.M.},
abstractNote = {An investigation has been undertaken into the creep behavior of the single-crystal superalloy CMSX-4. Creep deformation in the alloy occurs largely through dislocation activity in the {gamma} channels. Shearing of the {gamma}{prime} dislocations is observed, but at higher temperatures, this does not occur until late in life via the passage of superpartial dislocation pairs. At lower temperatures (1023 K) and high stress levels, shearing of the {gamma}{prime} precipitates is observed relatively early in the creep curve through the passage of {r_brace}111{l_brace}{l_angle}112{r_angle} dislocations, which leave superlattice stacking faults (SSFs) in the precipitates. The stress-rupture behavior of CMSX-4 has been modeled using a damage-mechanics technique, where the level of damage required to cause failure is defined by the effective stress reaching the material's ultimate tensile strength (UTS). This technique ensures that short-term rupture data extrapolate back to the UTS. High-temperature steady-state and tertiary creep are modeled using modified damage-mechanics equations, where the strain and damage rates are similar functions of stress. At intermediate operating temperatures of 1,023 and 1,123 K, the material exhibits pronounced sigmoidal primary creep of up to 4% strain, which cannot be modeled using a conventional approach. This transient behavior has been explained by the effect of internal stresses acting on dislocations in the gamma matrix; such an internal stress has been included in the creep law and evolves as a function of the damage-state variable.},
doi = {10.1007/s11661-000-0258-0},
journal = {Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science},
issn = {1073-5623},
number = 5,
volume = 31,
place = {United States},
year = {2000},
month = {5}
}