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Title: Local Electrode Atom Probe Characterization of Crept CMSX-4 Superalloy

Abstract

The solute distributions in crept and annealed single crystal CMSX-4 nickel-based superalloy have been characterized from multi-million atom data sets obtained with the local electrode atom probe. Solute-depleted and solute-enriched regions are evident on both sides of the - interface. Ultrafine (~1 nm diameter) rhenium clusters containing up to ~10-15% Re were evident in the 10-nm wide Reenriched region in the matrix close to the - interface. Re-enriched regions were also detected in asperities in the - interface in the crept conditions.

Authors:
 [1];  [2]
  1. ORNL
  2. Imperial College, London
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Shared Research Equipment Collaborative Research Center
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
936013
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: TMS Letters; Journal Volume: 3; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMS; ELECTRODES; HEAT RESISTING ALLOYS; MONOCRYSTALS; PROBES; RHENIUM; SOLUTES

Citation Formats

Miller, Michael K, and Reed, R. C. Local Electrode Atom Probe Characterization of Crept CMSX-4 Superalloy. United States: N. p., 2006. Web.
Miller, Michael K, & Reed, R. C. Local Electrode Atom Probe Characterization of Crept CMSX-4 Superalloy. United States.
Miller, Michael K, and Reed, R. C. Sun . "Local Electrode Atom Probe Characterization of Crept CMSX-4 Superalloy". United States. doi:.
@article{osti_936013,
title = {Local Electrode Atom Probe Characterization of Crept CMSX-4 Superalloy},
author = {Miller, Michael K and Reed, R. C.},
abstractNote = {The solute distributions in crept and annealed single crystal CMSX-4 nickel-based superalloy have been characterized from multi-million atom data sets obtained with the local electrode atom probe. Solute-depleted and solute-enriched regions are evident on both sides of the - interface. Ultrafine (~1 nm diameter) rhenium clusters containing up to ~10-15% Re were evident in the 10-nm wide Reenriched region in the matrix close to the - interface. Re-enriched regions were also detected in asperities in the - interface in the crept conditions.},
doi = {},
journal = {TMS Letters},
number = 1,
volume = 3,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • CMSX-4 superalloy laser beam welds were investigated by transmission electron microscopy and atom probe field-ion microscopy (APFIM). The weld microstructure consisted of fine (10- to 50-nm) irregularly shaped {gamma}' precipitates (0.65 to 0.75 volume fraction) within the {gamma} matrix. APFIM compositions of the {gamma} and {gamma}' phases were found to be different from those in the base metal. Concentration profiles across the {gamma} and {gamma}' phases showed extensive variations of Cr, Co and Al concentrations as a function of distance within the {gamma} phase. Calculated lattice misfits near the {gamma}/{gamma}' interface in the welds are positive values compared to themore » negative values for base metal.« less
  • No abstract prepared.
  • High temperature creep of nickel-based superalloy single crystals is characterized by directional coalescence of the {gamma}{prime} reinforcing precipitates. The morphology of the coalesced structures depends on experimental parameters such as the sense and direction of the creep stress as well as on intrinsic parameters such as the sign of the misfit between matrix and precipitates. For single crystals of the commercial superalloy CMSX-2 submitted to <100> creep at 1,323K, the initially cuboidal {gamma}{prime} precipitates coalesce into platelets arranged perpendicular or parallel to the stress direction when the stress is in tension or in compression, respectively. So far, however, the evolutionmore » of the local chemical composition around dislocations had not been experimentally investigated in nickel-based superalloys.« less
  • The purpose of this investigation was to study in detail the means to quantitatively evaluate {gamma}' phase precipitation. Many of the mechanical properties of superalloys are directly influenced by the presence of the {gamma}' (gamma prime) precipitate phase dispersed in a {gamma} matrix phase. The {gamma}' precipitates act as effective barriers to dislocation motion and restrict plastic deformation, particularly at high temperatures. Due to this, it is essential to accurately quantify the {gamma}' precipitate size, volume fraction and distribution. Investigations based on quantitative metallography and image analysis were performed on a monocrystalline nickel-base superalloy taking into consideration various {gamma}' precipitatemore » sizes present in that alloy microstructure. The authors of the present paper propose a new method of quantifying the total volume fraction of the {gamma}' phase applying images of the microstructure with {gamma}' phase precipitates registered using light microscopy, scanning electron microscopy (at two different magnifications) and scanning transmission electron microscopy.« less
  • 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 usingmore » 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.« less