Investigation of creep deformation mechanisms at intermediate temperatures in René 88 DT

Viswanathan, G.B.; Sarosi, Peter; Henry, Michael F.; Whitis, D.D.; Milligan, Walter W.; Mills, Michael J.

doi:10.1016/j.actamat.2005.03.017

Cited by 284 publications

(131 citation statements)

References 14 publications

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“…In the wake of the leading paired Shockley partials, a high energy, two-layer complex stacking fault (CSF) is created in the precipitate which must undergo atomic reordering in order to convert the pseudotwin structure to that of a true-twin, having the correct nearest neighbor atomic bonds for the ordered L1 2 structure of the γ′ phase. Further direct TEM evidence by Viswanathan et al [7,12] in Rene 88DT has substantiated Kolbe's original hypotheses by confirming that the twinning partial dislocations are indeed identical Shockley partials.…”

Section: Discussion Of Experimental Resultsmentioning

confidence: 63%

“…Microtwinning is another deformation mechanism that has been observed experimentally during high temperature creep in Ni-base superalloys [7,12,[17][18][19][20][21]. Kolbe first proposed that microtwins may form in a γ/γ′ strengthened superalloy by the motion of paired identical a/6<112> Shockley partial dislocations operating on adjacent {111} glide planes shearing both γ and γ′ [17].…”

Section: Discussion Of Experimental Resultsmentioning

confidence: 99%

“…It should be noted that this reordering process may also apply directly to other deformation mechanisms, such as the isolated faulting by superlattice extrinsic staking faults (SESFs) observed in Rene 88DT [7]. These reordering processes necessitate an atomic rearrangement in the wake of the partials to maintain the ordered L1 2 structure of the precipitates, which fundamentally explains the temperature and rate dependence during deformation in this regime.…”

Section: Atomistic Reorderingmentioning

confidence: 93%

“…Microtwinning was found to be the dominant mode of deformation. Characteristic of the microtwinning mechanism are highly planar faulted structures that shear both precipitate and matrix by a/6<112> type Shockley partial dislocations on adjacent {111} glide planes [7,12]. Figure 4b displays a BF TEM micrograph of the microtwins viewed nearly edge on with an inset selected area diffraction pattern directly on the [011] zone axis.…”

Section: Tertiary Creep Regime (∼10% Plastic Strain)mentioning

confidence: 99%

“…During high temperature creep deformation, the γ′ precipitates play a vital role in restricting plastic deformation as high energy configurations such as antiphase domain boundaries (APB), complex stacking faults (CSF), superlattice intrinsic stacking faults (SISF), and superlattice extrinsic stacking faults (SESF) develop if the precipitates were to be sheared by a/2<110> type perfect matrix dislocations, a/3<112> super-Shockley partial dislocations, or a/6<112> Shockley partial dislocations. There have been many detailed post mortem TEM characterization studies describing the deformation mechanisms responsible for creating such defect structures and implications they may have on controlling creep deformation for several different Ni-base superalloys [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Deformation Mechanisms in Ni-Base Disk Superalloys at Higher Temperatures

Kovařík¹,

Chen²,

Wang³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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This paper presents results from a research initiative aimed at investigating high temperature creep deformation mechanisms in Ni-base superalloys through a combination of creep experiments, TEM deformation mechanism characterization, and state of the art modeling techniques. The effect of microstructure on dictating creep rate controlling deformation mechanisms was revealed for specimens with a bimodal γ′ size distribution that possessed different secondary γ′ size, tertiary γ′ volume fraction, and γ channel width spacing. It was found that the less creep resistant microstructure was the one with a greater secondary γ′ size, wider γ channel width, and higher volume fraction of tertiary γ′. Deformation in this microstructure commences by way of a/2<110> dislocations concentrated in the γ matrix at lower strains, which then transition to a SISF precipitate shearing mode at larger strains. The more creep resistant microstructure possessed a finer γ channel width spacing, which promoted a/2<110> dislocation dissociation into a/6<112> Shockley partials at lower strains and microtwinning at higher strains. Dislocation precipitate interaction was further explored using microscopic phase field modeling, which was able to capture key microstructural aspects that can favor dislocation dissociation and decorrelation since this appears to be a precursor to the microtwinning deformation mode. New viable diffusion pathways associated with the reordering processes in microtwinning have been explored at the atomistic level. All of the above activities have shed light onto the complex nature of creep deformation mechanisms at higher temperatures.

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Section: Discussion Of Experimental Resultsmentioning

confidence: 63%

Section: Discussion Of Experimental Resultsmentioning

confidence: 99%

Section: Atomistic Reorderingmentioning

confidence: 93%

Section: Tertiary Creep Regime (∼10% Plastic Strain)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Deformation Mechanisms in Ni-Base Disk Superalloys at Higher Temperatures

Kovařík¹,

Chen²,

Wang³

et al. 2008

Superalloys 2008 (Eleventh International Symposium)

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A TEM Study of Creep Deformation Mechanisms in Allvac 718Plus

Unocic

Hayes³

et al. 2010

Superalloy 718 and Derivatives

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The Localization of Strain in Low Solvus High Refractory (LSHR) Nickel Superalloy

et al. 2012

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The low solvus high refractory (LSHR) nickel base superalloy was chosen as a candidate for a dual microstructure heat treatment (DMHT) turbine disk, with fine grains in the bore and coarser grains in the rim. In between those two regions, there is a transition in grain size and γ′ precipitation. In this study, the mechanical performance of the coarse grain region was evaluated by room temperature tensile testing in the un-aged and dual aged conditions. Optical digital image correlation (DIC) was used to detect the localized strains evolving from the tensile testing. Strain maps from the DIC successfully detected localized strains in both of the microstructural conditions of interest. Transmission and scanning electron microscopy was use to analyze the deformed regions to assess grain misorientation and dislocation activity within each microstructure. While dislocations appeared to accumulate in the gamma channels in both microstructures, there appeared to more grain misorientation in the unaged condition of LSHR.

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Investigation of creep deformation mechanisms at intermediate temperatures in René 88 DT

Cited by 284 publications

References 14 publications

Deformation Mechanisms in Ni-Base Disk Superalloys at Higher Temperatures

Deformation Mechanisms in Ni-Base Disk Superalloys at Higher Temperatures

A TEM Study of Creep Deformation Mechanisms in Allvac 718Plus

The Localization of Strain in Low Solvus High Refractory (LSHR) Nickel Superalloy

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