The role of interfacial dislocation networks in high temperature creep of superalloys

Gabb, Timothy P.; Draper, Susan L.; Hull, David R.; MacKay, Rebecca A.; Nathal, M. V.

doi:10.1016/0921-5093(89)90058-0

Cited by 171 publications

(69 citation statements)

References 15 publications

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“…In an ideal situation, with y'-rafts extending from one side of the crystal to the other in an almost perfectly regular manner, gliding/climbing around it by matrix dislocations is impossible. This conclusion is in accordance with opinions of other authors [ 1,13,21,23,24]. Another example for enhanced creep properties due to tensile pre-rafting can be found in [25].…”

Section: Introductionsupporting

confidence: 92%

“…70 %) of the ordered y'-phase (Ll;?-structure), which is coherently embedded in the fee y-matrix, are widely used as turbine blade material in aircrafts. In these hightemperature materials, so-called rafting (directional coarsening) has emerged as an important phenomenon both in laboratory tests [1,2,3] and in hot sections of turbine blades subjected to service conditions [4]. Furthermore, rafting has been observed after thermomechanical fatigue (TMF) [S].…”

Section: Introductionmentioning

confidence: 99%

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Enhancement of the High-Temperature Tensile Creep Strength of Monocrystalline Nickel-Base Superalloys by Pre-rafting in Compression

Tetzlaff¹,

Mughrabi²

2000

Superalloys 2000 (Ninth International Symposium)

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In recent years, the development of Y.-hardened monocrystalline nickel-base superalloys focused on different aspects of alloy composition and microstructural refinement. In particular, the formation of so-called y/y'-raft structures, lying typically, in the case of a negative y/y'-lattice misfit 6, perpendicular to the stress axis during high-temperature tensile creep had attracted much attention. Unfortunately, this microstructural transformation leads in most cases to deteriorated creep properties. Earlier attempts to prevent rafting by suitable prior annealing treatments had been in so far unsuccessful, that while the applied annealing treatment retarded raft formation, it inevitably lead to microstructural coarsening accompanied by creep acceleration. The goal of the present extensive study is to show that suitable pre-rafting in compression, leading to a y/y'-raft structure parallel to the stress axis in the case of a negative lattice misfit, enhances not only the isothermal hightemperature fatigue strength, as shown earlier, but also the hightemperature creep properties. The observed macroscopic creep behaviour will be discussed with reference of microstructural observations.

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Section: Introductionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Enhancement of the High-Temperature Tensile Creep Strength of Monocrystalline Nickel-Base Superalloys by Pre-rafting in Compression

Tetzlaff¹,

Mughrabi²

2000

Superalloys 2000 (Ninth International Symposium)

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“…The post-crept -' microstructure of UM-F11 is shown in Figure 3b to have sheared the ' precipitates. The dislocation substructure of the UM-F20 alloy is consistent with that reported for a number of commercial nickel-base superalloys [11,12,18,19].…”

Section: Solution Treated and Agedsupporting

confidence: 85%

“…Increased alloying with Re and W has resulted in superalloys with a negative -' lattice misfit, due to the strong partitioning behavior of these elements to the phase [7]. There has been much discussion in the literature regarding the relationship between the -' lattice misfit and the creep resistance of superalloys [8][9][10][11]. Though superalloys with a more negative misfit have generally been observed to be more creep resistant, a balance of properties, including solid solution strengthening of the matrix and strength of the ' are also important [12].…”

Section: Introductionmentioning

confidence: 99%

Microstructural Stability and Creep of Ru-Containing Nickel-Base Superalloys

Rowland¹,

Feng²,

Pollock³

2004

Superalloys 2004 (Tenth International Symposium)

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Nickel-base single crystal superalloys with Ru additions of 5.7 to 9.7 wt%, moderate amounts of refractory elements and up to 6.7 wt% Cr were investigated. The ' precipitate morphology of the experimental alloys was cuboidal, near-spherical and intermediately-shaped depending on the Cr and Ru content. The time to 1% creep and the creep rupture lives of the experimental alloys were measured at 950°C and 290 MPa. Within the set of alloys investigated rafting occurred parallel to the axis of the applied uniaxial tensile stress, perpendicular to the applied stress or was completely suppressed, suggesting a wide range of lattice misfit. Interfacial dislocation network development during creep also varied widely among the alloys investigated. The possibilities for control of microstructure and high temperature properties via Ru additions are discussed.

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“…This drastic morphological change of the γ' precipitates is called as rafting. Though the various models on the rafting mechanism have been proposed [7][8][9][10][11], the rafting mechanism has not been fully understood, especially the role of dislocation on the rafting mechanism has not been fully discussed yet. It was well understood that rafting of the γ/γ' structures strongly depends on the creep testing conditions, such as time, temperature and stress [11].…”

mentioning

confidence: 99%

Change in Gamma Prime Morphology and Dislocation Substructures of Single Crystal Nickel-Based Superalloy, CMSX-4, Pre-Crept at 1273K-400MPa with Simple Aging

Kondo

Miura

2011

AMR

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Abstract. The single crystal nickel-based superalloy, CMSX-4, creep interrupted at the creep strain of 0.01 at 1273K-400MPa was aged at 1273K without stress to make clear the γ/γ' rafting mechanism. And the changes in the γ' morphology and the dislocation substructures at the γ/γ' interface with simple aging time were studied and compared with the previous work at 1273K-250MPa. The cuboidal γ' precipitates were regularly arrayed when the creep test was interrupted, but changed to the rafted γ/γ' structures normal to the pre-creep stress axis with simple aging time. The aspect ratio of the γ' precipitates increased with increasing simple aging time up to 3.60x10 6 s, attained to the maximum value and then decreased. The maximum value of the aspect ratio at 400MPa was lower than one at 250MPa. A number of dislocations were tangled with each other at the γ/γ' interfaces of the creep interrupted specimen. These tangled dislocations were only rearranged by simple aging and the dislocation density at the γ/γ' interfaces was almost constant, independent of simple aging time. All dislocations of the creep interrupted specimen at the γ/γ' interfaces with six kinds of the <110> Burgers vectors were detected equally. The proportion of the six kinds of the <110> Burgers vectors didn't change with simple aging time. Consequently, dislocations at the γ/γ' interfaces were considered as not the misfit ones, but the traces of mobile dislocations in the γ channels and the formation of the rafted γ/γ' structures might be closely correlated with the rearrangement of tangled dislocations at the γ/γ' interfaces. IntroductionThe cuboidal γ' precipitates in the single crystal nickel-based superalloys with the stress axis of the [001] orientation turn its shape into the plate like ones perpendicular to the stress axis during high temperature creep deformation [1][2][3][4][5][6]. This drastic morphological change of the γ' precipitates is called as rafting. Though the various models on the rafting mechanism have been proposed [7][8][9][10][11], the rafting mechanism has not been fully understood, especially the role of dislocation on the rafting mechanism has not been fully discussed yet. It was well understood that rafting of the γ/γ' structures strongly depends on the creep testing conditions, such as time, temperature and stress [11]. These factors make it difficult to clarify the rafting mechanisms. In our previous work, the single crystal nickel-based superalloy interrupted at the creep strain of 0.01 at 1273K-250MPa was aged at 1273K without stress and the changes in the γ' morphology and the dislocation substructures at the γ/γ' interfaces with simple aging time were studied. The nearly cuboidal γ' precipitates were regularly arrayed when the creep test was interrupted, but changed to the rafted γ/γ' structures with simple aging time. A number of dislocations which were tangled with each other at the γ/γ' interfaces of the creep interrupted specimen were only rearranged by simple aging and the dislocation density at the interfaces...

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The role of interfacial dislocation networks in high temperature creep of superalloys

Cited by 171 publications

References 15 publications

Enhancement of the High-Temperature Tensile Creep Strength of Monocrystalline Nickel-Base Superalloys by Pre-rafting in Compression

Enhancement of the High-Temperature Tensile Creep Strength of Monocrystalline Nickel-Base Superalloys by Pre-rafting in Compression

Microstructural Stability and Creep of Ru-Containing Nickel-Base Superalloys

Change in Gamma Prime Morphology and Dislocation Substructures of Single Crystal Nickel-Based Superalloy, CMSX-4, Pre-Crept at 1273K-400MPa with Simple Aging

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